Anderson, Richard A.

Treatment-induced ovarian function loss is a significant concern for many young patients with breast cancer. Accurately predicting this risk is crucial for counselling young patients and informing their fertility-related decision-making. However, current risk prediction models for treatment-related ovarian function loss have limitations. To provide a broader representation of patient cohorts and improve feature selection, we combined retrospective data from six datasets within the FoRECAsT (Infertility after Cancer Predictor) databank, including 2679 pre-menopausal women diagnosed with breast cancer. This combined dataset presented notable missingness, prompting us to employ cross imputation using the k-nearest neighbours (KNN) machine learning (ML) algorithm. Employing Lasso regression, we developed an ML model to forecast the risk of treatment-related amenorrhea as a surrogate marker of ovarian function loss at 12 months after starting chemotherapy. Our model identified 20 variables significantly associated with risk of developing amenorrhea. Internal validation resulted in an area under the receiver operating characteristic curve (AUC) of 0.820 (95% CI: 0.817–0.823), while external validation with another dataset demonstrated an AUC of 0.743 (95% CI: 0.666–0.818). A cutoff of 0.20 was chosen to achieve higher sensitivity in validation, as false negatives—patients incorrectly classified as likely to regain menses—could miss timely opportunities for fertility preservation if desired. At this threshold, internal validation yielded sensitivity and precision rates of 91.3% and 61.7%, respectively, while external validation showed 92.9% and 60.0%. Leveraging ML methodologies, we not only devised a model for personalised risk prediction of amenorrhea, demonstrating substantial enhancements over existing models but also showcased a robust framework for maximally harnessing available data sources.

Abstract STUDY QUESTION How should premature/primary ovarian insufficiency (POI) be diagnosed and managed based on the best available evidence from published literature? SUMMARY ANSWER The current guideline provides 145 recommendations on symptoms, diagnosis, causation, sequelae, and treatment of POI. WHAT IS KNOWN ALREADY Premature ovarian insufficiency (POI) presents a significant challenge to women’s health, with far-reaching implications, both physically and emotionally. The potential implications include adverse effects on quality of life; fertility; and bone, cardiovascular, and cognitive health. Although hormone therapy (HT) can mitigate some of these effects, many questions still remain regarding the optimal management of POI. STUDY DESIGN, SIZE, DURATION The guideline was developed according to the structured methodology for development of ESHRE guidelines. Key questions were determined by a group of experts and informed by a scoping survey of women and health care professionals. Literature searches and assessments were then performed. Papers published up to 30 January 2024 and written in English were included in the guideline. An integrity review was conducted for the randomized controlled trials (RCTs) on POI included in the guideline. PARTICIPANTS/MATERIALS, SETTING, METHODS Based on the collected evidence, recommendations were formulated and discussed within the guideline development group until consensus was reached. Women with lived experience of POI informed the recommendations in general, and particularly on those on provision of care. A stakeholder review was organized after finalization of the draft. The final version was approved by the guideline development group and the ESHRE Executive Committee. MAIN RESULTS AND THE ROLE OF CHANCE New data indicate a higher prevalence of POI, 3.5%, than was previously thought. This guideline aims to help health care professionals to apply best practice care for women with POI. The recent update of the POI guideline covers 40 clinical questions on diagnosis of the condition, the different sequelae, including bone, cardiovascular, neurological and sexual function, fertility and general well-being, and treatment options, including HT. The list of clinical questions was expanded from the previous iteration of the guideline (2015) based on the scoping survey and appreciation of emerging knowledge of POI. Questions were added on the role of anti-Müllerian hormone (AMH) in the diagnosis of POI, fertility preservation, muscle health, and specific considerations for HT in iatrogenic POI. Additionally, the topic on complementary treatments was extended with specific focus on non-hormonal treatments and lifestyle management options. Significant changes from the previous 2015 guideline include the recommendations that only one elevated FSH >25 IU is required for diagnosis of POI, and guidance that AMH testing, repeat FSH measurement, and/or AMH may be required where there is diagnostic uncertainty. Recommendations were also updated regarding genetic testing, estrogen doses and regimens, use of the combined oral contraceptive and testosterone therapy. Women with lived experience of POI informed the recommendations on provision of care. LIMITATIONS, REASONS FOR CAUTION The guideline describes different management options, but it must be acknowledged that for most of these options, supporting evidence is limited for POI. WIDER IMPLICATIONS OF THE FINDINGS The guideline provides health care professionals with clear advice on best practice in POI care, based on the best evidence currently available. In addition, a list of research recommendations is provided to guide further studies in POI. STUDY FUNDING/COMPETING INTEREST(S) The guideline was developed and funded by ESHRE, American Society for Reproductive Medicine (ASRM), Centre for Research Excellence in Women's Health in Reproduction Life (CRE-WHiRL), and International Menopause Society (IMS), covering expenses associated with the guideline meetings, literature searches, and dissemination of the guideline. The guideline group members did not receive payments. N.P. declared grants from Bayer Pharma (research and consultancy) and NIHR—research POISE; consulting fees from Abbott, Astellas, Bayer, Besins, Lawley, Mithra, Theramex, Viatris; honoraria from Astellas, Bayer, Besins, Gedeon Richter, Theramex, Viatris; support for attending meetings and/or travel from Astellas, Bayer, Theramex, Viatris; President, International Menopause Society, Medical Advisory Committee member, British Menopause Society, Patron Daisy Network. A.J.V. declared grants from Amgen Australia, Australian NHMRC, and Australian MRFF; consulting fees from IQ Fertility; honoraria from the Australasian Menopause Society; participation on a Data Safety Monitoring Board or Advisory Board of Astellas; Board Member of the International Menopause Society (2020 to current) and Past president of the Australasian Menopause Society (2017–2019); R.A.A. declared grants from Roche (Research support, to institution), and participation on a Data Safety Monitoring Board of Bayer. M.C. declared grants from NHI; payments or honoraria from Up-to-Date (as editor/reviewer); Board Member of American Society of Reproductive Medicine, and of American Gynecological and Obstetrical Society. M.D. declared (NIHR—HTA Reference Number: NIHR133461; NIHR—HTA Reference Number: NIHR128757; Action Medical Research and Borne: GN2818) consulting fees from a small personal medical practice, support for attending meetings and/or travel from ESHRE, Bayer and UCLH special Trustees; Participation on the Advisory Board of the British Menopause Society, UKSTORE project, the Progress Educational Trust, and the Turner Syndrome Support Society UK; Leadership or fiduciary roles in the British Fertility Society (Trustee), Elizabeth Garrett Anderson Hospital Charity (chair of Trustees), and the Essex Wynter charitable trust (Trustee). C.E. declared being Chair of a SIG from the Royal Australian College of General Practitioners Integrative Medicine Specific Interest Group and Program Lead for Next Practice Western Sydney Integrative Health. C.H.G. declared grants from Novo Nordisk Foundation (Nos. NNF15OC0016474 and NNF20OC0060610), sygesikringen danmark (No 2022-0189), and the Independent Research Fund Denmark (Nos. 0134-00406 and 0134-00130B); consulting fees from Novo Nordisk, Merck, and Astra Zeneca. S.K. declared grants from Roche diagnostics. A.K. declared grants from NIH R01 5R01HD101475; consulting fees as Medical Reviewer for Flo and for Healthline; honoraria as Medical Consultant for Summus; support for attending meetings from the Reproductive Scientist Development Program; Society for Reproductive Investigation Council Member and Society for Assisted Reproduction Registry/Validation Chair; R.E.N. declared consulting fees from Astellas, Bayer Pharma, Besins Healthcare, Fidia, Theramex; honoraria from Abbott, Astellas, Exeltis, Fidia, Gedeon Richter, Merck & Co, Novo Nordisk, Shionogi Limited, Theramex, Viatris; payment for expert testimony from Vichy Laboratories; Participation in Data Safety Monitoring Board of Advisory board from Astellas and Bayer Healthcare; President elect of the International Menopause Society (IMS). H.T. declared a grant from NHMRC Centre for Research Excellence for women’s health in reproductive life. A.B. declared being chair of the Daisy Network Charity. The other authors have no conflicts of interest to declare. DISCLAIMER This guideline represents the views of ESHRE, ASRM, CRE-WHiRL, and IMS, which were achieved after careful consideration of the scientific evidence available at the time of preparation. In the absence of scientific evidence on certain aspects, a consensus between the relevant stakeholders has been obtained. Adherence to these clinical practice guidelines does not guarantee a successful or specific outcome, nor does it establish a standard of care. Clinical practice guidelines do not replace the need for application of clinical judgement to each individual presentation, nor variations based on locality and facility type. The collaborating societies make no warranty, expressed or implied, regarding the clinical practice guidelines and specifically exclude any warranties of merchantability and fitness for a particular use or purpose. (Full disclaimer available at www.eshre.eu/guidelines.)

Abstract Premature ovarian insufficiency (POI) presents a significant challenge to women's health, with significant implications both physically and emotionally. Despite its life-altering impact, there remain substantial unknowns in the causes this condition and how to optimally manage its various sequelae While such unknows provide direction for future research, they also underscore the need for clinical guidance. In 2015, under the auspices of ESHRE, a group of experts evaluated the existing best evidence and published the first European guideline on the management of premature ovarian insufficiency. The update of this Guideline was performed in an international collaboration of experts representing American Society for Reproductive Medicine (ASRM), International Menopause Society (IMS), and the Centre for Research Excellence in Women’s Health in Reproductive Life (CRE WHiRL). The recent update of the POI guideline covers 40 clinical questions on diagnosis of the condition, the different sequelae, including musculoskeletal health, cardiovascular health, neurological health, sexual function and general well being, and treatment options, including hormone therapy. The list of clinical questions was expanded from the questions included in the guideline from 2015. Based on a scoping survey and appreciation of emerging knowledge of POI, questions were added on the role of AMH in the diagnosis of POI, fertility preservation, muscle health, and specific considerations for hormone treatment in iatrogenic POI. Additionally, the topic on complementary treatments was extended with specific focus on non-hormonal treatments and lifestyle management options. The draft guideline published for stakeholder review includes a total of 142 recommendations. One third of these recommendations were formulated as good practice points. Of the evidence-based recommendations, almost 80% were formulated as strong recommendations, even if the evidence base for most evidence-based recommendations was limited to observational data (level very low or low), supporting a call for future research. The guideline group hope that the new POI Guideline will improve the clinical management of this devastating condition.

Background: The potential gonadotoxicity of anti-HER2 agents remains largely unknown, and limited, conflicting evidence exists for taxanes. Antimüllerian hormone (AMH) is an established biomarker of ovarian reserve that may aid in quantifying anticancer treatment–induced gonadotoxicity. Patients and Methods: The present biomarker analysis of the randomized phase III neoadjuvant NeoALTTO trial included premenopausal women aged ≤45 years at diagnosis of HER2-positive early breast cancer with available frozen serum samples at baseline (ie, before anticancer treatments), at week 2 (ie, the “biological window” of anti-HER2 therapy alone), and/or at the time of surgery (ie, after completing paclitaxel + anti-HER2 therapy, before starting adjuvant chemotherapy). Results: The present analysis included 130 patients with a median age of 38 years (interquartile ratio [IQR], age 33–42 years). AMH values at the 3 time points differed significantly (P<.001). At baseline, median AMH levels were 1.29 ng/mL (IQR, 0.56–2.62 ng/mL). At week 2, a small but significant reduction in AMH levels was observed (median, 1.10 ng/mL; IQR, 0.45–2.09 ng/mL; P<.001). At surgery, a larger significant decline in AMH levels was observed (median, 0.01 ng/mL; IQR, 0.01–0.03 ng/mL; P<.001). Although the type of anti-HER2 treatment (trastuzumab and/or lapatinib) did not seem to impact the results, age and pretreatment ovarian reserve had a major influence on treatment-induced gonadotoxicity risk. Conclusions: This NeoALTTO biomarker analysis showed that anti-HER2 therapies alone had limited gonadotoxicity but that the addition of weekly paclitaxel resulted in marked AMH decline with possible negative implications for subsequent ovarian function and fertility.

PURPOSE Many patients and physicians remain concerned about the potential detrimental effects of pregnancy after breast cancer (BC) in terms of reproductive outcomes and maternal safety. This systematic review and meta-analysis aimed at providing updated evidence on these topics. METHODS A systematic literature review was conducted to identify studies including patients with a pregnancy after BC (PROSPERO number CRD42020158324). Likelihood of pregnancy after BC, their reproductive outcomes, and maternal safety were assessed. Pooled relative risks, odds ratios (ORs), and hazard ratios (HRs) with 95% CIs were calculated using random effects models. RESULTS Of 6,462 identified records, 39 were included involving 8,093,401 women from the general population and 112,840 patients with BC of whom 7,505 had a pregnancy after diagnosis. BC survivors were significantly less likely to have a subsequent pregnancy compared with the general population (relative risk, 0.40; 95% CI, 0.32 to 0.49). Risks of caesarean section (OR, 1.14; 95% CI, 1.04 to 1.25), low birth weight (OR, 1.50; 95% CI, 1.31 to 1.73), preterm birth (OR, 1.45; 95% CI, 1.11 to 1.88), and small for gestational age (OR, 1.16; 95% CI, 1.01 to 1.33) were significantly higher in BC survivors, particularly in those with previous chemotherapy exposure, compared with the general population. No significantly increased risk of congenital abnormalities or other reproductive complications were observed. Compared to patients with BC without subsequent pregnancy, those with a pregnancy had better disease-free survival (HR, 0.66; 95% CI, 0.49 to 0.89) and overall survival (HR, 0.56; 95% CI, 0.45 to 0.68). Similar results were observed after correcting for potential confounders and irrespective of patient, tumor, and treatment characteristics, pregnancy outcome, and timing of pregnancy. CONCLUSION These results provide reassuring evidence on the safety of conceiving in BC survivors. Patients' pregnancy desire should be considered a crucial component of their survivorship care plan.

Abstract Background: Pregnancy-related issues are a priority for young breast cancer (BC) patients. Increasing evidence has shown that pregnancy after prior BC diagnosis is feasible. Nevertheless, few BC survivors conceive following anticancer treatment completion and many physicians remain concerned about the potentially detrimental effects of pregnancy after BC in terms of fetal/obstetrical outcomes and maternal prognosis. This systematic review and meta-analysis aims at providing updated and solid evidence on these important issues. Methods: A systematic literature review up to January 31, 2020 with no language restriction was conducted to identify studies including patients with a pregnancy after prior BC diagnosis. Chances of pregnancy after BC, fetal and obstetrical outcomes, disease-free survival (DFS) and overall survival (OS) were assessed. Pooled relative risks (RRs), hazard ratios (HRs) or odds ratio (ORs) with 95% confidence intervals (CI) were calculated using the random effects models. The study is registered with the PROSPERO registration number CRD42020158324. Results: Overall, 39 studies were included. Out of the 8,265,713 young women included in these studies, 8,093,401 were from the general population, 57,739 had cancers other than BC, 114,573 had BC. Among the 114,573 BC patients, 7,505 had a pregnancy after BC diagnosis and 107,068 did not. Compared to women from the general population, BC patients had 60% reduced chances of having a pregnancy following anticancer treatment completion (RR 0.40, 95% CI 0.32-0.49). Among other cancer patients, only women with prior cervical cancer had lower pregnancy rates (RR 0.33, 95% CI 0.31-0.35) than BC patients. Compared to the general population, BC survivors had significantly increased risks of low birth weight (OR 1.50, 95% CI 1.31-1.73), small for gestational age (OR 1.16, 95% CI 1.01-1.33), preterm delivery (OR 1.45, 95% CI 1.11-1.88) and caesarean section (OR 1.14, 95% CI 1.04-1.25). No significant increased risk of congenital abnormalities (OR 1.63, 95% CI 0.89-2.98) or other pregnancy or delivery complications (spontaneous or induced abortion, gestosis, antepartum or postpartum hemorrhage) was observed. Prior chemotherapy exposure or short pregnancy interval (defined as &lt;2 or &lt;5 years after BC diagnosis) were not associated with additional increased risk of complications. Pregnancy after BC was not associated with a negative impact on patients’ outcomes. Compared to BC patients without subsequent pregnancy, those with pregnancy after BC had better OS (HR 0.56, 95% CI 0.46-0.67) and DFS (HR 0.73, 95% CI 0.56-0.94). Similar results were observed in the studies correcting for the potential “healthy mother effect” (OS: HR 0.52, 95% CI 0.42-0.65; DFS: HR 0.74, 95% CI 0.58-0.96). No detrimental prognostic effect of pregnancy after BC was observed in patients with hormone-receptor positive disease (DFS: HR 1.10, 95% CI 0.73-1.66), while better outcomes were observed for those with hormone-receptor negative disease (DFS: HR 0.72, 95% CI 0.55-0.95). The safety of pregnancy after BC was observed irrespective of BRCA status, nodal status, previous chemotherapy exposure, pregnancy interval and pregnancy outcomes. Conclusions: This large meta-analysis provides solid evidence on the safety of pregnancy after prior BC diagnosis. The increased risk of fetal and obstetrical complications (but not of congenital abnormalities) calls for ensuring a closer monitoring of these pregnancies. The significantly reduced chances of conceiving as compared to the general population and other cancer patients should raise further awareness on the need to improve the oncofertility counseling of young BC patients wishing to complete their family planning following anticancer treatment completion. Citation Format: Eva Blondeaux, Marta Perachino, Marco Bruzzone, Richard A. Anderson, Evandro De Azambuja, Philip D. Poorvu, Hee Jeong Kim, Cynthia Villarreal-Garza, Barbara Pistilli, Ines Vaz-Luis, Cristina Saura, Kathryn J. Ruddy, Maria Alice Franzoi, Chiara Sertoli, Marcello Ceppi, Hatem A. Azim, Jr., Frederic Amant, Isabelle Demeestere, Lucia Del Mastro, Ann H. Partridge, Olivia Pagani, Fedro A. Peccatori, Matteo Lambertini. Chances of pregnancy after breast cancer, reproductive and disease outcomes: A systematic review and meta-analysis [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS3-09.

Abstract STUDY QUESTION What is the role of the hypothalamic neuropeptide neurokinin B (NKB) and its interaction with kisspeptin on GnRH/LH secretion in women with polycystic ovary syndrome (PCOS)? SUMMARY ANSWER Administration of neurokinin 3 receptor antagonist (NK3Ra) for 7 days reduced LH and FSH secretion and LH pulse frequency in women with PCOS, whilst the stimulatory LH response to kisspeptin-10 was maintained. WHAT IS KNOWN ALREADY PCOS is characterized by abnormal GnRH/LH secretion. NKB and kisspeptin are master regulators of GnRH/LH secretion, but their role in PCOS is unclear. STUDY DESIGN, SIZE, DURATION The NK3Ra MLE4901, 40 mg orally twice a day, was administered to women with PCOS for 7 days (n = 8) (vs no treatment, n = 7). On the last day of NK3Ra administration or the equivalent day in those not treated, women were randomized to 7-h kisspeptin-10 (4 µg/kg/h i.v.) or vehicle infusion. This was repeated with the alternate infusion in a subsequent cycle. PARTICIPANTS/MATERIALS, SETTING, METHODS Subjects were women with PCOS, studied in a Clinical Research Facility. Reproductive hormones were measured before and after NK3Ra administration. On the last day of NK3Ra administration (or the equivalent cycle day in untreated women), all women attended for an 8-h frequent blood sampling to allow analysis of the pulsatile LH secretion. MAIN RESULTS AND THE ROLE OF CHANCE NK3Ra reduced LH secretion (4.0 ± 0.4 vs 6.5 ± 0.8 IU/l, P &lt; 0.05) and pulse frequency (0.5 ± 0.1 vs 0.8 ± 0.1 pulses/h, P &lt; 0.05); FSH secretion was also reduced (2.0 ± 0.3 vs 2.5 ± 0.4 IU/l, P &lt; 0.05). Without NK3Ra pre-treatment, kisspeptin-10 increased LH secretion (5.2 ± 0.5 to 7.8 ± 1.0 IU/L, P &lt; 0.05), with a positive relationship to oestradiol concentrations (r2 = 0.59, P &lt; 0.05). After NK3Ra administration, the LH response to kisspeptin-10 was preserved (vehicle 3.5 ± 0.3 vs 9.0 ± 2.2 IU/l with kisspeptin-10, P &lt; 0.05), but the positive correlation with oestradiol concentrations was abolished (r2 = 0.07, ns. after NK3Ra). FSH secretion was increased by kisspeptin-10 after NK3Ra treatment, but not without NK3Ra treatment. LIMITATIONS, REASONS FOR CAUTION The study did not explore the dose relationship of the effect of NK3R antagonism. The impact of obesity or other aspects of the variability of the PCOS phenotype was not studied due to the small number of subjects. WIDER IMPLICATIONS OF THE FINDINGS These data demonstrate the interactive regulation of GnRH/LH secretion by NKB and kisspeptin in PCOS, and that the NKB system mediates aspects of oestrogenic feedback. STUDY FUNDING/COMPETING INTEREST(S) Wellcome Trust through Scottish Translational Medicine and Therapeutics Initiative (102419/Z/13/A) and MRC grants (G0701682 to R.P.M. and R.A.A.) and MR/N022556/1 to the MRC Centre for Reproductive Health. This work was performed within the Edinburgh Clinical Research Facility. J.T.G. has undertaken consultancy work for AstraZeneca and Takeda Pharmaceuticals and is an employee of Boehringer Ingelheim. R.P.M. has consulted for Ogeda and was CEO of Peptocrine. R.A.A. has undertaken consultancy work for Merck, Ferring, NeRRe Therapeutics and Sojournix Inc. J.D.V. and K.S. have nothing to disclose. TRIAL REGISTRATION NUMBER N/A.

Abstract Context Neurokinin B (NKB) is obligate for human puberty, but its role in adult female gonadotropin secretion and ovarian follicle growth is unknown. Objective To investigate antagonism of NKB on pulsatile gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion and ovarian follicle development in healthy women. Design Open investigation of the effects of a neurokinin-3 receptor (NK3R) antagonist (NK3Ra) vs a no-treatment control cycle. Setting Clinical research facility. Patients or other participants Healthy women with regular menses (n = 13). Intervention(s) NK3Ra MLE4901 40 mg taken orally twice daily from cycle day 5 to 6 for 7 days. Main outcome measure(s) LH secretion, ovarian follicle growth, and timing of ovulation. Results NK3Ra administration reduced basal LH secretion without a change in pulse frequency and delayed the LH surge by 7 days, the duration of treatment [mean cycle day ± standard error of the mean (SEM), 22 ± 1 days vs 15 ± 1 days in control cycles; P = 0.0006]. Follicle growth (mean diameter at the end of administration of NK3Ra administration ± SEM, 9.3 ± 0.4 mm vs 15.1 ± 0.9 mm in control cycles; P &lt; 0.0001) and rising estradiol concentrations (mean ± SEM, 166 ± 29 pmol/L vs 446 ± 86 pmol/L in control cycles; P &lt; 0.0001) were prevented. After treatment, follicle development resumed and normal preovulatory follicle diameter and estradiol concentrations were demonstrated. Postovulatory progesterone rise was similarly delayed (peak cycle day, 30 ± 2 vs 22 ± 1; P = 0.002) and cycle length was prolonged (35 ± 1 days vs 29 ± 1 days in control cycles; P = 0.0003) but luteal progesterone excretion was unaffected by the NK3Ra (LH surge day +7 mean urinary progesterone levels ± SEM, 58 ± 10 pmol/mol vs 48±7 pmol/mol creatinine in control cycles; nonsignificant). Conclusion These data demonstrate the involvement of NKB-NK3R signaling in the physiological regulation of GnRH/LH secretion, determining normal follicle development in women.

SummaryObjectivePatients with mutations of neurokinin B (NKB) and its receptor show hypogonadotrophic hypogonadism, but there is little evidence for the importance of this pathway in reproductive function in normal men, or its functional hierarchy with kisspeptin.DesignAn open label study wherein men (n = 6) were administered the NK3R antagonist MLE4901 40 mg orally twice a day for 7 days. Kisspeptin‐10 (0.3 μg/kg iv bolus) was given before and on day 7 of NK3R antagonist treatment.PatientsSubjects were healthy men.MeasurementsReproductive hormones were measured before and during the NK3R antagonist administration, including frequent sampling on two occasions for analysis of pulsatile LH secretion.ResultsLH, FSH and testosterone secretion were decreased during NK3R antagonist administration. LH showed a biphasic response, being reduced after 24 hours of treatment (4.5 ± 0.6 IU/L pretreatment to 1.7 ± 0.2 IU/L, P < .05), with partial recovery thereafter, but it was again decreased on day 7 (2.5 ± 0.6 IU/L, P < .05 vs pretreatment). FSH secretion was also suppressed, with a similar temporal pattern to that of LH. Testosterone secretion was decreased from 24 hours (18.4 ± 1.6 pretreatment vs 5.6 ± 1.5 nmol/L, P < .01) and remained suppressed throughout the treatment period. Analysis of LH pulsatility showed that both basal and pulsatile LH secretion were markedly suppressed but there was no detected change in LH pulse frequency. Kisspeptin‐10 stimulated LH secretion, with similar responses before and during NK3R antagonist administration.ConclusionsThese data demonstrate a central role for NKB/NK3R in the physiological regulation of reproductive function in men, and that this is functionally upstream of kisspeptin‐mediated GnRH secretion.