„Peptides for women” is a broad search term on the internet, not a specific scientific or medical category. Depending on the context, it can refer to preparations containing dietary peptides, peptide ingredients used in cosmetics, compounds studied in the context of reproductive hormones, or specific drugs that are peptides or peptide-like compounds.
These categories should not be treated as equivalent.
Evidence that a specific preparation containing collagen peptides affects a specific parameter during resistance training does not mean that a peptide associated with the reproductive system produces the same effect. A prescription drug study in premenopausal women with a specific disorder does not demonstrate overall benefits for all women. Similarly, the result regarding reproductive hormones cannot be automatically transferred to menopause, fertility, pregnancy, breastfeeding, body composition, skin appearance, or healthy aging.
There are studies involving women on various interventions related to peptides. These include, among other things, studies of specific collagen preparations, kisspeptin in reproductive physiology and assisted reproductive procedures, and controlled studies of bremelanotide in women before menopause with a specific sexual desire disorder. [1] [2] [3]
However, these studies concerned fundamentally different results.
They cannot be combined into a single general statement that peptides improve „female hormones,” fertility, the course of menopause, libido, body composition, or processes related to aging.
The studied population is also of great importance. Women before menopause, in the peri-menopausal period, after menopause, pregnant women, breastfeeding women, patients undergoing infertility treatment, and women with specific endocrine or sexual health disorders constitute different study populations.
In this article, we explain why these differences are important, how to interpret claims about peptides directed at women, what human studies actually measure, and why safety during pregnancy and breastfeeding requires separate data.
The article is of an educational and scientific informational nature. It does not recommend any peptide, product, treatment, dosage, route of administration, or protocol of use. The regulatory examples cited are subject to jurisdiction.
Why are evidence regarding a specific gender important?
The clinical study primarily describes the population that was actually examined.
If only men participated in the study, its results can provide valuable biological information, but by themselves they do not allow us to determine the magnitude of the effect, the profile of adverse reactions, or the consequences related to the female reproductive system.
This does not mean that women and men must react differently to each peptide or intervention.
However, if the statement is specifically directed at women, similarities should not simply be assumed.
Reproductive physiology, natural hormonal patterns, body composition, age, simultaneous exposure to hormones, the possibility of pregnancy, and other factors can influence both the research question and the interpretation of the results.
Even if both women and men participate in the study, the mere presence of women does not yet necessarily mean strong evidence specific to women.
It is worth checking how many women participated in the study, whether the results were analyzed separately, whether the reproductive life stage was determined, and whether the sample size allowed for a reliable assessment of potential differences.
The average result for both sexes may properly describe the entire studied population, while leaving significant uncertainty regarding a smaller subgroup of women.
Can the results of studies conducted on men be automatically applied to women?
No. Studies in men can provide valuable information regarding biological mechanisms and form the basis for further hypotheses, but they do not themselves establish the same magnitude of effect, adverse reaction profile, or reproductive consequences in women. If the claim is directed directly at women, it should, to the extent possible, be supported by appropriate studies in this population, and if indirect evidence is used, the scope of extrapolation should be clearly indicated.
Women do not constitute a homogeneous research population
The term „women” can encompass several biologically and clinically distinct populations.
The pre-menopause period, perimenopause, the post-menopause period, pregnancy and lactation are associated with various physiological conditions.
The chronological age alone does not replace information regarding the reproductive life stage.
Two women of similar age can differ significantly in terms of menstrual cycle, natural hormonal exposure, contraceptive use, infertility treatment, menopausal status, and hormonal menopause therapy.
The clinical situation also matters.
Healthy women with regular menstrual cycles constitute a different population than women undergoing assisted reproductive procedures.
Women experiencing menopausal symptoms differ from those who were eligible for the study due to reduced bone mineral density.
Women with a recognized sexual desire disorder constitute another clinical population.
The results obtained in one of these groups should not be automatically presented as evidence regarding all women.
The terminology used by the authors of the original study should also be observed. The publication may define participants based on menstrual cycles, reproductive criteria, diagnosis, age, or other clinical characteristics, without describing all variables that could influence the possibility of generalizing the results.
The review of the evidence should therefore describe the population as it was actually studied, rather than filling in the missing information with assumptions.
The phase of the menstrual cycle can affect the hormonal response
The menstrual cycle is a direct example of why the reproductive context can matter.
In a study involving women with regular menstrual cycles, kisspeptin-54 was analyzed and it was found that the gonadotropin response differed depending on the phase of the cycle. In particular, the luteinizing hormone response, or LH, was stronger in the preovulatory period.[4]
This is direct evidence that the hormonal environment present at the time of the study can influence the measured response to a signal related to the reproductive system.
This does not mean that manipulating this response leads to overall improvement in health.
It, however, shows why uncontrolled comparison of the participants studied at different stages of the cycle can lead to interpretational difficulties.
If one group is evaluated during a phase in which the reproductive system reacts more strongly naturally, and the other during a phase of lower reactivity, part of the difference attributed to the intervention may actually result from the initial physiological conditions.
In endocrinological studies, it is therefore useful to take into account the reproductive life stage, the phase of the cycle, the use of hormonal contraception or other essential medications, and the time of performing biological measurements.
If these factors are not described or controlled, there remains uncertainty as to whether the observed difference results from intervention, natural physiological variability, or a combination of both factors.
Why might the phase of the menstrual cycle be relevant in peptide studies?
The hormonal environment changes during the menstrual cycle and can influence the body’s response to signals related to the reproductive system. A study of kisspeptin-54 showed that the LH response differed depending on the phase of the cycle and was stronger during the preovulatory phase.[4] This does not mean that each peptide acts differently in different phases of the cycle, but it does show the importance of standardizing the measurement time and accurate reporting in endocrine studies.
Studies of libido require a clearly defined clinical question
The term „female libido peptide” is much broader than clinical studies involving a specific drug.
An important example is the RECONNECT program, which includes two randomized, double-blind, placebo-controlled studies of bremelanotide in premenopausal women with hypoactive sexual desire disorder.
In total, 1,267 women were randomized in both studies. In the controlled period, improvements in assessed sexual desire and a reduction in distress associated with low desire were observed. Adverse effects, including nausea, skin redness, and headache, occurred more frequently in the bremelanotide group than in the placebo group.[3]
These results represent data from human studies regarding a specific intervention in a strictly defined clinical population.
They do not prove an overall increase in sexual performance in every woman.
They do not confirm such an effect in women without the disorder being examined.
They should also not be automatically transferred to women after menopause or interpreted as evidence regarding fertility.
Current U.S. information regarding the product Vyleesi specifies a limited indication for women before menopause and does not indicate this drug for women after menopause or for increasing sexual performance.[5]
This shows why the very word „libido” is not sufficient to assess the claim regarding peptides.
Diagnosis, the reproductive life stage, intervention, comparator, evaluated outcome, study time, and the regulatory status specific to the given jurisdiction all influence the interpretation.
Does improving libido mean improving fertility?
No. Sexual desire and fertility are separate outcomes. The studies of bremelanotide measured sexual desire and related distress, whereas the kisspeptin studies on sexual stimulus processing analyzed brain responses and psychometric and hormonal measurements. [2] [3] None of these studies confirm an improvement in the probability of conception or live birth simply because they involve sexual or reproductive biology.
A mechanistic study of sexual response answers another question
The studies of kisspeptin are another example of how seemingly similar experiments can answer completely different questions.
In a placebo-controlled cross-sectional study, kisspeptin was evaluated in 40 premenopausal women with hypoactive sexual desire disorder. Thirty-two participants completed both study visits. Brain responses to erotic and facial attractiveness-related stimuli were analyzed, as well as psychometric and hormonal results. [2]
This type of study can provide valuable information regarding the mechanisms involved in the processing of sexual stimuli.
However, it does not automatically lead to a lasting improvement in daily sexual functioning.
It does not confirm an improvement in fertility.
It does not provide evidence regarding women after menopause.
Short research visits also do not allow the determination of long-term safety.
The mechanistic response seen in an imaging or laboratory study can help to understand the action of a particular biological pathway. However, demonstrating lasting clinical benefit requires a different type of study, including appropriate functional results and a sufficiently long observation period.
Claims regarding menopause require the indication of a specific result.
The term „menopause-related peptides” is scientifically too broad, unless it is known what effect it is intended to have.
Menopause-related studies can analyze vasomotor symptoms such as hot flashes, sleep, sexual symptoms, bone mineral density, body composition, physical fitness, mood, skin condition, or quality of life.
These results are not equivalent.
Reducing the amount of fat tissue does not prove to relieve the effects of heat.
A change in the mineral density of the bones does not confirm an improvement in sleep.
A positive result regarding skin appearance does not mean that hormone levels are normalized throughout the body.
Improvement in sexual desire is not evidence of protection against osteoporosis.
A term like „supports menopause” therefore contains too little information to be scientifically evaluated.
A significant claim should specify a specific intervention, a stage of the reproductive life cycle, a measured endpoint, and the evidence supporting that outcome.
The training study in women before menopause is not a study of menopausal treatment.
A good example is a randomized study of specific collagen peptides used in conjunction with resistance training.
Seventy-seven women before menopause completed a 12-week training program. The study noted favorable differences between the groups in selected body composition parameters and grip strength. Body composition was estimated using electrical bioimpedance, and the participants in both groups performed resistance training. [1]
The results are relevant for the specific nutritional supplement, the population being studied, the measurement methods used, and the training conditions.
They do not confirm the treatment of menopausal symptoms.
They do not indicate the normalization of reproductive hormones.
They also do not indicate that a pharmacological peptide administered in a different way will produce the same effects simply because both interventions are referred to as peptides.
The measurement method is also important.
Estimation of lean body mass using bioimpedance is not equivalent to direct measurement of newly formed muscle tissue.
Similarly, improvements in grip strength should not automatically be interpreted as an improvement in all parameters of strength or physical fitness.
The interpretation should remain linked to what was actually measured.
Bone studies in postmenopausal women answer another question
Studies conducted after menopause provide another example of the importance of specific endpoints.
In a 12-month randomized study of a specific collagen peptide preparation, 131 postmenopausal women with decreased bone mineral density with age participated. Compared to placebo, beneficial changes in measured bone mineral density and selected markers of bone turnover were observed. [6]
This is a direct study conducted in a population of postmenopausal women.
The evaluated results concerned, however, primarily the bones.
The study did not show a reduction in all symptoms of menopause.
It did not confirm the normalization of estrogen levels.
It also did not show a reduction in the number of fractures as a clinical endpoint.
The mineral density of the bone is an important parameter, but it is not the same thing as the frequency of fractures.
Confirmation of fracture prevention would require an appropriate evaluation of clinical events and a sufficiently long observation period.
The intervention itself is also important.
The study concerned a specific oral nutritional supplement. The results cannot be used to confirm the action of an unrelated injectable product, a package offered by a clinic, or any other compound simply because the word „peptide” also appears in its marketing.
Does an improvement in bone mineral density mean fewer fractures?
No. Bone mineral density is an important measure, but it is not the same endpoint as fracture incidence. The study of collagen peptides in postmenopausal women included, among other things, bone density and markers of bone turnover. [6] Demonstrating a reduction in the number of fractures requires an appropriate study of clinical events and the observation period. Therefore, a distinction must be made between the change in an indirect bone parameter and the reported reduction in the risk of fractures.
Body composition, physical fitness, and menopausal symptoms should be analyzed separately
Body weight, amount of adipose tissue, lean mass, skeletal muscle mass, strength, physical fitness, and the severity of symptoms are different outcomes.
They can influence each other, but they do not have to change at the same time.
Interventions affecting one parameter should not automatically be attributed to improvements in the others.
The change in estimated non-fat mass, for example, does not indicate an improvement in menopausal symptoms.
The change in grip strength does not confirm the normalization of hormones.
Weight loss does not necessarily mean muscle preservation.
Similarly, improving one symptom of menopause does not mean a beneficial change in body composition.
Studies of older people or mixed-gender populations can provide useful general information, but the age range alone does not confirm a menopausal status.
The claim regarding specifically postmenopausal women has the strongest basis when the study actually identifies the reproductive stage and measures the outcome associated with that stage.
Without such precision, the term „for women” can become much broader than the available evidence suggests.
In a similar way, one should approach claims regarding body composition and weight reduction. In the article about peptides for weight loss we discuss why body mass, fat tissue, appetite, and body composition are separate outcomes that should not be treated as synonyms.
Cosmetic peptides and systemic effects require further evidence
Peptides are also often used in cosmetics.
A topical preparation containing a peptide can be tested for skin hydration, wrinkle visibility, elasticity, tolerance, and other dermatological effects.
The results relate to a specific formulation of the cosmetic product and the measured skin effect.
They do not confirm an overall effect on the reproductive system.
They do not indicate an improvement in fertility.
They do not show changes in body composition or in the concentration of circulating reproductive hormones.
The route of administration is an important part of this distinction.
Evidence regarding the formulation used topically does not automatically indicate safety, systemic exposure, or efficacy of the product administered by any other route, even if it contains a similarly named ingredient.
The reverse rule also applies.
Systemic studies do not automatically confirm that a topical cosmetic formulation leads to the same biological exposure.
The identity of the component also requires careful verification.
If the search term contains an abbreviation, an alternative spelling, a trade name, or a possible error, before attributing scientific evidence, it is necessary to determine what substance is actually involved.
An unclear term should not be replaced without explanation with evidence regarding another peptide.
In the case of cosmetic applications, it is worth separately analyzing a specific skin problem. For example, we discuss available studies and limitations regarding skin prone to irritation in the article about peptides for sensitive and acne-prone skin.
Reproductive signaling is not the same as effective infertility treatment
Fertility is not a single biological event.
The studies can measure hormone secretion, the development of ovarian follicles, the maturation of oocytes, ovulation, fertilization, embryo development, implantation, clinical pregnancy, ongoing pregnancy, or live birth.
These are different stages of the reproductive process.
Measurable increases in reproductive hormone can indicate that a given biological pathway is responding to stimulation.
However, it does not prove that ovulation occurred.
Even effective ovulation does not guarantee fertilization.
Similarly, proper maturation of the oocyte does not guarantee fertilization, implantation, pregnancy, or a live birth.
The summary of the evidence should therefore maintain exactly the same endpoint as that actually measured.
The denominator used to calculate the result also matters.
The pregnancy rate calculated for embryo transfer does not mean the same thing as the pregnancy rate among all participants who were originally included in the study.
Not every person starting a fertility study will reach the stage of egg collection, embryo formation, transfer, pregnancy, or live birth.
A change in the denominator can therefore significantly change the apparent percentage value.
Does the increase in reproductive hormones indicate ovulation or pregnancy?
No. The hormonal response is only one stage of a much more complex process. In the multiple exposure study of kisspeptin, a gonadotropin response was initially observed, which decreased with subsequent administrations, and in the described ultrasound measurements of reproductive activity, no significant changes were noted. [8] Ovulation, fertilization, pregnancy, and live birth should be measured directly, rather than inferred based on a short-term hormonal response.
Kisspeptin was studied under controlled conditions in reproductive medicine
Kisspeptin is an important example of a peptide studied directly in reproductive medicine.
60 women undergoing in vitro fertilization participated in the Phase 2 study, where the risk of ovarian hyperstimulation syndrome was considered high. The researchers analyzed kisspeptin-54 as part of an oocyte maturation strategy in specialized infertility treatment conditions and recorded subsequent reproductive outcomes. [7]
In the study, no moderate, severe, or critical ovarian hyperstimulation syndrome was observed. [7]
This is a clinically important observation.
The scope of the proposals must, however, remain clearly defined.
The study included a strictly defined population of women undergoing IVF in a specialized program.
The project involved randomization between experimental levels of exposure, rather than demonstrating superiority over all existing interventions used in the treatment of infertility.
The number of trials also limits the possibility of excluding rare adverse reactions.
The results therefore support a specific research question regarding the maturation of oocytes dependent on kisspeptin in women with an increased risk of ovarian hyperstimulation syndrome.
They do not confirm kisspeptin as a universal fertility-improving agent.
They also do not specify the effectiveness or safety of use outside of specialized reproductive medicine care.
Can IVF studies be applied automatically to all people trying to have a child?
No. IVF research is conducted within the framework of specialized reproductive medicine procedures and often involves carefully selected populations. The study of oocyte maturation using kisspeptin involved women considered to be at high risk of ovarian hyperstimulation syndrome.[7] The results therefore directly relate to this specific research context. Their application to natural attempts at pregnancy or to all patients treated for infertility would require additional data.
The immediate hormonal response does not have to persist
Another experiment involving kisspeptin shows why an immediate endocrine response should not be automatically interpreted as a lasting effect related to fertility.
In a small randomized study of women with hypothalamic amenorrhea, a strong gonadotropin response to kisspeptin was initially observed.
However, under repeated administration, the response weakened. No significant changes were also observed in the ultrasound-described parameters of reproductive activity. [8]
This result is of great conceptual importance.
The biological pathway may react strongly to the first stimulus, but it does not have to maintain the same response with repeated exposure.
The reasoning that „the relationship stimulates reproductive hormones, so it improves fertility” is therefore incomplete.
The first part can be demonstrated experimentally, while the second remains unconfirmed.
The claim regarding fertility requires data covering the relevant stages of the reproductive process and a period long enough to measure the declared result.
Different causes of infertility require different evidence.
Infertility itself is a very heterogeneous phenomenon.
Fertility problems can have many different causes.
The signaling of reproductive hormones, ovarian reserve, ovulation disorders, ovarian factors, uterine factors, sperm parameters, age-related changes, and other circumstances create different clinical questions.
Interventions studied in one of these contexts cannot be automatically generalized to others.
Even within the IVF procedures, the qualification criteria and the protocols used are important.
A study selecting women based on a high risk of ovarian hyperstimulation syndrome does not necessarily represent all patients treated for infertility.
The most useful evidence therefore identifies a specific reproductive problem, the context of the treatment, the population, and the outcome.
The general label „fertility peptide” cannot replace this information.
Pregnancy requires separate safety data
Pregnancy constitutes a separate research question.
The absence of reported harm in a small number of pregnancies exposed to the specified substance does not prove its safety during pregnancy.
A rare adverse effect may simply not occur in a small sample.
Incomplete observation can also lead to the omission of parts of the results.
Pregnancy safety encompasses much more than visible birth defects.
Miscarriages, fetal growth, complications in the mother, premature birth, neonatal outcomes, and potentially also the later development of the child can be significant.
Different results require different numbers of trials and observation durations.
A study that does not show a statistically significant increase in a specific event therefore does not confirm the absence of all possible risks associated with pregnancy.
The interpretation is influenced by the sample size, the confidence intervals, the moment of exposure, its intensity and duration, the mother's health status, and the comparison group.
Does the lack of reported adverse effects mean that the substance is safe during pregnancy?
No. Small trials, incomplete observation, limited range of evaluated outcomes, and a short observation period may not detect rare or delayed risks. A prospective study of exposure to GLP-1 receptor agonists provided reassuring information regarding the analyzed exposures in early pregnancy, but in the case of some results the estimates remained poorly precise, and the authors pointed to the need for larger studies. [9] The absence of a detected safety signal is scientific information, but it is not evidence of the exclusion of any possible risk.
Observational data on pregnancy can be reassuring, but not conclusive
In a prospective multicenter study, 168 pregnancies were observed in which exposure to GLP-1 receptor agonists occurred in the first trimester.
The researchers used comparison groups comprising people with diabetes and overweight or obese individuals, and in the analyses conducted they did not detect an increased risk of serious birth defects or pregnancy loss. [9]
These are useful data involving people.
They can reduce uncertainty, especially in situations of unintentional exposure at the beginning of pregnancy.
However, the study does not confirm universal safety during pregnancy.
Estimates regarding congenital defects were not very precise, and the authors pointed to the need for larger studies.[9]
This was an observational study, not a randomized trial of the intentional, continuous use of the intervention throughout the entire pregnancy.
The analysis of the entire group also does not prove identical safety for each GLP-1 receptor agonist, each exposure level, or each stage of pregnancy.
A balanced interpretation therefore is that the study did not detect an increased risk for the analyzed outcomes, but there are still significant areas of uncertainty.
This is not equivalent to either stating that harm has been demonstrated or proving that full safety has been demonstrated.
The moment of exposure during pregnancy matters
The moment of exposure is particularly important when evaluating data regarding pregnancy.
Brief exposure before pregnancy diagnosis is biologically different from continuous exposure in later stages of pregnancy.
Individual periods of development are associated with different physiological processes.
Therefore, studies should, as far as possible, identify the moment of exposure instead of grouping all cases into one category.
The comparative population is also important.
Diseases that occur in the mother can independently affect the results of pregnancy.
Comparing women with diabetes to the general population without diabetes, for example, may introduce differences in baseline risk that are not directly related to the substance being studied.
Statistical adjustment and carefully selected comparison groups can mitigate this problem, but in observational studies, some interference may still remain.
The reassuring observational result should therefore remain linked to a specific population and exposure period.
It should not be turned into a general statement about the safety of the entire class of substances during pregnancy.
Breastfeeding requires a different kind of evidence
Lactation creates a different route of exposure than pregnancy.
Researchers may need to determine whether the parent substance or its relevant metabolites pass into the milk, what concentrations are present over time, how much milk the infant consumes, what portion of the substance can be absorbed by the infant, and whether any biological effects occur.
Results regarding the mother may also be significant, including the potential impact on milk production and its nutritional status.
In a small study of semaglutide, samples of the milk of eight women were analyzed.
Using the analytical method employed, the researchers did not detect semaglutide in the samples collected and estimated the potential exposure of the infant under certain assumptions. However, they also drew attention to unresolved questions regarding long-term outcomes and nutritional aspects. [10]
These are valuable analytical data.
The term „undetectable” does not mean, however, that the concentration was mathematically equal to zero.
This means that the substance was not detected above the detection limits of the method used in the analyzed samples.
The study also included only eight women.
Therefore, it cannot determine the safety for every age of the infant, every state of the mother's health, the method of exposure, the time of use, or the formulation.
Does „undetected in the mother's milk” mean exactly zero exposure of the child?
No. „Undetected” means that the analytical method used did not detect the substance above its detection limit in the analyzed samples. The study of semaglutide in female milk included eight women and left unanswered questions regarding long-term results. [10] This is valuable information regarding the penetration into milk under certain conditions, but not evidence of mathematically zero exposure or universal safety for infants.
Data from the pregnancy period do not replace data regarding breastfeeding.
Pregnancy and breastfeeding are associated with different routes of biological exposure.
During pregnancy, fetal exposure is related to the physiology of the mother and placental transport.
During breastfeeding, the concentrations of substances in the mother's blood are important, as is their passage into the milk, the amount of milk consumed by the baby, absorption in the infant's digestive tract, metabolism, and the susceptibility of the baby's body.
Evidence from one period therefore does not automatically answer questions about another period.
The reassuring results of the pregnancy study do not indicate how the substance passes into the milk.
Similarly, the non-detection of the substance in a small number of milk samples does not confirm its safety for the fetus during pregnancy.
The route of administration and the formulation still matter.
Results regarding oral, topical or injectable preparations should not be automatically transferred to another formulation if the systemic exposure differs.
If the evidence is incomplete, the appropriate approach is to clearly present the uncertainties, rather than providing assurance about safety just because a given substance is described as a „peptide”.
Individual questions regarding exposure during pregnancy or breastfeeding require an assessment of the specific substance, formulation, time of exposure, and clinical situation by an appropriately qualified health care professional.
The studied population determines how far the results can be generalized
The correct interpretation starts with the question of who actually participated in the study.
The useful description includes age, reproductive life stage, diagnosis, relevant medications, the place of conducting the study, and the most important inclusion and exclusion criteria.
These characteristics define the population that the results describe most directly.
For example, the studies of bremelanotide included a strictly defined population of premenopausal women. The publications also reported that the majority of participants were white, and the recruitment took place in centers in the United States.[3]
This does not invalidate the results.
It, however, describes the population to which the evidence most directly refers.
However, the mere statement that women participated in the study does not prove uniform efficacy or safety across different stages of the reproductive life cycle, ethnic groups, health conditions, geographic populations, or with different formulations.
Therefore, generalizing the results beyond the studied population requires appropriate caution.
The participation of women in the study does not automatically mean the analysis is specific to women.
A study involving both sexes can include women while providing a less precise estimate of the effect in this group.
The information about the number of participating women is only the beginning.
The study must also provide appropriate statistical data to assess whether the effect among women has been estimated with sufficient precision.
Formal analyses of interactions can be more informative than a simple statement that one subgroup obtained a statistically significant result and the other did not.
A statistically significant result in one group and an insignificant one in the other does not automatically prove that the groups reacted differently.
One of the subgroups might simply have included fewer participants and had a lower statistical power.
The same principle applies to the individual stages of the reproductive life cycle.
Assessments regarding women before and after menopause require appropriate characteristics and analysis, not assumptions based solely on age.
The length of the observation period and the participants' resignations influence the interpretation of long-term data.
Longer observation is valuable, but the way it is conducted must also be taken into account.
Individuals who continue to participate in an expanded study may systematically differ from those who quit.
Participants who have a poor tolerance to treatment may be less likely to remain in the study.
Those who benefit from it, however, may be more willing to continue using it.
Such phenomena may affect estimates of long-term efficacy and safety.
An example is the open-label extension of the bremelanotide study.
Of the eligible participants, 684 decided to enter the extended phase, and 272 completed it. The prerequisite for eligibility was also the completion of the previous phase without serious adverse events.[11]
In the extended phase, no new safety signal was identified. [11]
This is useful information.
This phase included a selected population, did not have the same continuous, blinded comparison with placebo, and featured a significant outflow of participants.
Therefore, it should not be treated as a counterpart to a large, long-term randomized safety study.
Longer observation increases the amount of available data, but the research project still determines the strength of the conclusions.
The result of the study must correspond to the formulated claim
If the study shows an improvement in the sexual desire score, the corresponding claim concerns the desire or associated distress in the studied population. It does not independently confirm an improvement in fertility, ovulation, the probability of fertilization, or the safety of pregnancy.
If IVF shows that the oocytes have matured properly, the application concerns precisely this stage of the reproductive process. It does not prove a universal improvement in fertility or guarantee pregnancy or a live birth.
If a study of postmenopausal women shows a beneficial change in bone mineral density, the result applies to the bones. It does not prove a reduction in hot flashes, sleep problems, mood disturbances, sexual symptoms, or any of the other symptoms associated with menopause.
If resistance training testing shows changes in body composition, the results pertain to parameters measured within this training protocol. They do not confirm overall hormonal normalization or a universal improvement in physical fitness.
If no substance is detected in the analytical study of lactation in several samples of milk, the correct conclusion is that the substance was not detected using the given method and under the specified sampling conditions. This does not mathematically mean zero exposure of the child or complete long-term safety.
Similarly, the absence of an adverse event in a small cohort indicates what was observed in this particular trial. It does not prove that all possible reproductive or developmental hazards have been excluded.
Maintaining a relationship between the measurement and the formulated claim is one of the most important principles of evaluating evidence regarding peptides in women.
Frequently asked questions about peptides for women
Do „peptides for women” mean one type of treatment?
No. The term may include dietary peptides, cosmetic ingredients, compounds studied in reproductive physiology, and specific prescription medications. These interventions fundamentally differ in structure, route of administration, biological target, exposure, intended use, and level of evidence. The study of collagen peptides during resistance training and the study of bremelanotide regarding sexual desire demonstrate this difference well.[1][3] The assessment should therefore begin with a specific intervention and claim, rather than with a general category of „peptides for women”.
Can a study of premenopausal women confirm the benefits during menopause?
Not directly. Both the reproductive life stage and the measured outcome are relevant. The study of collagen peptides and resistance training included women before menopause and addressed parameters assessed during a 12-week exercise program. [1] It did not examine treatment of menopausal symptoms. The results should therefore remain relevant to the study population, the preparation, and the training context.
Does successful maturation of oocytes guarantee a live birth?
No. Oocyte maturation is only one stage of assisted reproduction. Later, fertilization, embryo development, transfer, implantation, and the subsequent course of pregnancy follow. The kisspeptin study in IVF presented different reproductive outcomes separately, and some indicators were calculated using different nomenclature.[7] Therefore, the success of the intermediate stage does not guarantee the final outcome in the form of a live birth.
Do the reassuring results of pregnancy monitoring justify the intentional use of the substance throughout the entire pregnancy?
Such a conclusion cannot be drawn solely from observational data regarding early exposure. The GLP-1 receptor agonist cohort included exposure in the first trimester and encompassed a limited number of cases for evaluation of rare outcomes. [9] Such data may be useful in assessing accidental early exposure, but they do not confirm the safety of any compound, later stages of pregnancy, prolonged exposure, or intentional continuation throughout the entire pregnancy.
Can studies in pregnancy confirm the safety during breastfeeding?
No. Pregnancy and lactation are associated with different exposure pathways and other outcomes. The GLP-1 receptor agonist exposure study in the first trimester and the semaglutide study in female milk correspond to two different questions. [9] [10] Data from pregnancy may provide a useful background, but the assessment of breastfeeding requires its own information regarding passage to breast milk, the potential exposure of the child, absorption, effects on the mother, and relevant clinical outcomes.
Are the results regarding peptides used topically and in other ways interchangeable?
No. The route of administration and formulation strongly influence exposure. A cosmetic product applied topically and tested for its effects on the skin does not confirm an overall systemic effect on the reproductive system. Meanwhile, results regarding systemic interventions cannot be automatically attributed to a cosmetic product simply because similar peptide names appear on both labels. Claims should remain linked to the exactly tested formulation and result.
Does the mere inclusion of women in a study mean strong evidence regarding women?
No. The participation of women only confirms that they were included in the study population. It does not automatically mean a precise assessment of efficacy or safety in this group. Adequate sample size, characteristics of the reproductive phase, appropriate endpoints, and appropriate analysis are required. The studies of bremelanotide are an example of a project involving a clearly defined population of premenopausal women [3].
Does the open-label extension of the study confirm long-term safety?
No. Extended-duration phases can provide valuable long-term data, but selection bias, lack of blinding, lack of continuous comparison with placebo, and attrition can affect the results. In the bremelanotide extension phase, 684 eligible participants chose to continue participation, and 272 completed the phase. [11] The absence of new safety signals is an important information within the scope of this project, but it does not prove that rare, delayed, or long-term adverse effects do not occur.
Which question is the most important when evaluating the claim about „the peptide for women”?
The most useful question is: was this intervention actually tested in women in the appropriate reproductive life stage and was such an outcome measured that the claim is based on? A training study, a fertility treatment study, a libido study, a pregnancy cohort, and a lactation study all answer different questions.[1][3][7][9][10] A reliable summary of the evidence should maintain these boundaries and clearly indicate when the data are indirect, preliminary, restricted to a specific population, or incomplete.
Limitations of available evidence
The first significant limitation is the vast breadth of the category itself. Dietary supplements containing collagen, peptides involved in reproductive signaling, peptide and peptide-like drugs, cosmetic ingredients, and metabolic drugs should not be grouped together as one evidence category just because they all may appear in a search containing the word „peptide.”.
The second limitation is the specificities of the reproductive life stage. The pre-menopause period, perimenopause, the post-menopause period, pregnancy and breastfeeding constitute different biological situations. Evidence from one period does not automatically determine efficacy or safety in another.
The third is the necessity of precisely determining the outcome. Libido, hormone secretion, oocyte maturation, pregnancy, live birth, mineral density of the bone, body composition, skin appearance, and substance penetration into the milk are different endpoints.
The fourth limitation is the fact that the indirect biological result does not necessarily correspond to the final clinical result. The increase in hormone does not prove pregnancy. Ovum maturation does not guarantee a live birth. An improvement in bone mineral density does not automatically prevent fractures. The absence of a substance in the milk does not confirm the child's complete safety.
The fifth problem is the small number of participants or the strong selection of participants in some studies. Such projects can provide valuable data, while leaving uncertainty regarding rare adverse effects, the possibility of generalizing the results and the long-term results.
The sixth limitation is the particular difficulty in interpreting studies on pregnancy and breastfeeding. Observational data, accidental exposures, small sample sizes, different exposure times, and co-morbidities in the mother can all influence the results.
Seventhly, the significance of the formulation and the route of administration are important factors. The result obtained for a specific oral nutritional supplement does not confirm the action of the non-injectable product, similarly to the evidence regarding the locally applied cosmetic product does not confirm the systemic effect on the reproductive system.
Finally, the regulatory status depends on the specific intervention and jurisdiction. The approval of a single peptide drug or peptide-like drug for a precisely defined population of women does not mean the approval of other peptides or the existence of a broad regulatory category of „peptides for women.”.
Summary
There are real human studies of peptide and peptide-like interventions in women, but there is no single scientific category in which all „peptides for women” have common application, evidence, benefits, or safety profile.
Specific preparations of collagen peptides have been studied in specific nutritional and training contexts, including during resistance training in premenopausal women and with respect to bone parameters in postmenopausal women.[1][6] The results should remain relevant to these preparations, populations, and endpoints, rather than being generalized to unrelated pharmacological peptides.
Studies of kisspeptin show that the response of the reproductive system may depend on the phase of the menstrual cycle, and the compound itself has also been studied under strictly controlled conditions of infertility treatment. [4] [7] At the same time, repeated exposure studies show why a short-term hormonal response should not be automatically interpreted as a lasting reproductive benefit. [8]
Bremelanotyd is an example of a peptide-like drug supported by controlled clinical trials in a narrowly defined population of premenopausal women with hypoactive sexual desire disorder.[3] The results do not confirm a universal increase in sexual performance, improvement in fertility, or benefits in postmenopausal women, and the regulatory indication remains limited to a specific population.[5]
Pregnancy and breastfeeding require even greater interpretative caution. A prospective cohort study on GLP-1 receptor agonist exposure in the first trimester showed no increased risk in the analyzed results, but the precision of the data was limited and the study did not confirm universal safety in pregnancy. [9] In a small study on semaglutide absorption into breast milk, no substance was detected in the analyzed samples using the method used, but this does not mean mathematically zero exposure or confirmed long-term safety for the infant. [10]
In each of these areas, the same basic principle applies: precise intervention, a specific population, the reproductive life stage, the route of administration, formulation, comparator, and the measured outcome determine what can actually be inferred from the available evidence.
„Peptides for women” may be a useful search term, but they do not constitute a scientifically uniform category of treatment.
Menopause, sexual desire, fertility, pregnancy, breastfeeding, body composition, bone health, and cosmetic effects should remain separate research questions. Results from one area should not be used to confirm another simply because both involve women and a substance called a peptide.
The same principle of dividing specific results applies in other areas of research on peptides. For example, an article about Peptides and sleep, memory and brain function It shows why the results regarding sleep, anxiety, a neurological biomarker, or cognitive function should not be treated as evidence of a single general „brain effect”.
Disclaimer
The article is for educational and scientific informational purposes only. It does not constitute medical advice, recommendations regarding the treatment of infertility or menopause, instructions regarding pregnancy or breastfeeding, information on prescribing medications, dosage recommendations, instructions for administration, or recommendations for the use of any peptide, peptide drug, peptide-like substance, dietary supplement, or experimental substance.
The discussed evidence relates to specific populations, formulations, routes of administration, study designs, and evaluated outcomes. Results should not be automatically transferred between premenopausal and postmenopausal women, patients treated for infertility, and the general population, pregnancy and breastfeeding, dietary and pharmacological preparations, or topical and systemic formulations.
Pregnancy, breastfeeding, treatment of infertility, menstrual irregularities, symptoms of menopause, problems related to sexual health, and endocrine disorders require individual clinical evaluation. Decisions regarding such situations should be discussed with a suitably qualified health care professional.
References
- Jendricke, P., Centner, C., Zdzieblik, D., Gollhofer, A., & König, D. (2019). Specific collagen peptides in combination with resistance training improve body composition and regional muscle strength in premenopausal women: A randomized controlled trial. Nutrients, 11(4), 892. https://doi.org/10.3390/nu11040892
- Thurston, L., Hunjan, T., Ertl, N., Wall, M. B., Mills, E. G., Suladze, S., Patel, B., Alexander, E. C., Muzi, B., Bassett, P. A., Rabiner, E. A., Bech, P., Goldmeier, D., Abbara, A., Comninos, A. N., & Dhillo, W. S. (2022). Effects of kisspeptin administration in women with hypoactive sexual desire disorder: A randomized clinical trial. JAMA network open, 5(10), e2236131. https://doi.org/10.1001/jamanetworkopen.2022.36131
- Kingsberg, S. A., Clayton, A. H., Portman, D., Williams, L. A., Krop, J., Jordan, R., Lucas, J., & Simon, J. A. (2019). Bremelanotide for the treatment of hypoactive sexual desire disorder: Two randomized phase 3 trials. Obstetrics and gynecology, 134(5), 899–908. https://doi.org/10.1097/AOG.0000000000003500
- Dhillo, W. S., Chaudhri, O. B., Thompson, E. L., Murphy, K. G., Patterson, M., Ramachandran, R., Nijher, G. K., Amber, V., Kokkinos, A., Donaldson, M., Ghatei, M. A., & Bloom, S. R. (2007). Kisspeptin-54 stimulates gonadotropin release most potently during the preovulatory phase of the menstrual cycle in women. The Journal of clinical endocrinology and metabolism, 92(10), 3958–3966. https://doi.org/10.1210/jc.2007-1116
- Cosette Pharmaceuticals, Inc. (2025). Vyleesi—bremelanotide injection [Prescribing information]. DailyMed. Vyleesi—bremelanotide injection [Prescribing information]
- König, D., Oesser, S., Scharla, S., Zdzieblik, D., & Gollhofer, A. (2018). Specific collagen peptides improve bone mineral density and bone markers in postmenopausal women—A randomized controlled study. Nutrients, 10(1), 97. https://doi.org/10.3390/nu10010097
- Abbara, A., Jayasena, C. N., Christopoulos, G., Narayanaswamy, S., Izzi-Engbeaya, C., Nijher, G. M., Comninos, A. N., Peters, D., Buckley, A., Ratnasabapathy, R., Prague, J. K., Salim, R., Lavery, S. A., Bloom, S. R., Szigeti, M., Ashby, D. A., Trew, G. H., & Dhillo, W. S. (2015). Efficacy of kisspeptin-54 to trigger oocyte maturation in women at high risk of ovarian hyperstimulation syndrome (OHSS) during in vitro fertilization (IVF) therapy. The Journal of clinical endocrinology and metabolism, 100(9), 3322–3331. https://doi.org/10.1210/jc.2015-2332
- Jayasena, C. N., Nijher, G. M., Chaudhri, O. B., Murphy, K. G., Ranger, A., Lim, A., Patel, D., Mehta, A., Todd, C., Ramachandran, R., Salem, V., Stamp, G. W., Donaldson, M., Ghatei, M. A., Bloom, S. R., & Dhillo, W. S. (2009). Subcutaneous injection of kisspeptin-54 acutely stimulates gonadotropin secretion in women with hypothalamic amenorrhea, but chronic administration causes tachyphylaxis. The Journal of clinical endocrinology and metabolism, 94(11), 4315–4323. https://doi.org/10.1210/jc.2009-0406
- Dao, K., Shechtman, S., Weber-Schoendorfer, C., Diav-Citrin, O., Murad, R. H., Berlin, M., Hazan, A., Richardson, J. L., Eleftheriou, G., Rousson, V., Diezi, L., Haefliger, D., Simões-Wüst, A. P., Addor, M. C., Baud, D., Lamine, F., Panchaud, A., Buclin, T., Girardin, F. R., & Winterfeld, U. (2024). Use of GLP1 receptor agonists in early pregnancy and reproductive safety: a multicenter, observational, prospective cohort study based on the databases of six Teratology Information Services. BMJ open, 14(4), e083550. https://doi.org/10.1136/bmjopen-2023-083550
- Diab, H., Fuquay, T., Datta, P., Bickel, U., Thompson, J., & Krutsch, K. (2024). Subcutaneous semaglutide during breastfeeding: Infant safety regarding drug transfer into human milk. Nutrients, 16(17), 2886. https://doi.org/10.3390/nu16172886
- Simon, J. A., Kingsberg, S. A., Portman, D., Williams, L. A., Krop, J., Jordan, R., Lucas, J., & Clayton, A. H. (2019). Long-term safety and efficacy of bremelanotide for hypoactive sexual desire disorder. Obstetrics and gynecology, 134(5), 909–917. https://doi.org/10.1097/AOG.0000000000003514