First large trial of tirzepatide in PCOS begins enrolling in Germany
A 198-woman German trial is the first large randomized test of whether tirzepatide changes menstrual bleeding and ovulation in PCOS, with results not expected before late 2028.
The University of Bonn, working with four collaborating centers in Germany, has begun enrolling participants in PERIODS, a randomized, double-blind, placebo-controlled phase 4 trial of tirzepatide in women with polycystic ovary syndrome (PCOS) [1]. The study, registered as NCT07326111, is designed to enroll 198 premenopausal women aged 18 to 45 who have a body mass index of at least 27 and a PCOS diagnosis made using the Rotterdam criteria [1]. Enrollment opened on December 9, 2025 [1].
Treatment in the trial lasts 72 weeks [1]. The first 20 weeks are a dose-escalation phase, during which participants move up to the highest dose of tirzepatide they can tolerate; the following 52 weeks are a maintenance phase at that dose [1]. Because the study is placebo-controlled and double-blind, some participants receive a placebo, and neither the participants nor the investigators know who is receiving which [1].
The primary endpoint is the ratio of menstrual bleeding over the final 52 weeks of the trial [1]. The key secondary endpoint is the number of ovulations, confirmed by weekly blood tests for serum progesterone [1]. The record does not state what size of change in the bleeding ratio would count as a success, and it does not give a target number of ovulations. It also does not disclose how many participants will receive tirzepatide compared with placebo [1].
Tirzepatide is sold in the United States as Mounjaro and Zepbound. The registered trial does not report any earlier randomized study of the drug in PCOS, which is why this one is being described by its investigators as testing reproductive function and metabolic health together in this group [1].
Why it matters for patients
PCOS is not among the conditions GLP-1 and related medications are approved to treat, and this trial has not reported results, so it is not known whether tirzepatide improves bleeding patterns or ovulation in women with PCOS [1]. Anyone taking tirzepatide for weight or diabetes and also managing PCOS has no trial evidence from this study to draw on yet.
The endpoints chosen here are narrower than weight loss. Menstrual bleeding and confirmed ovulation are specific reproductive measures, and a drug can change weight or blood sugar without changing either one [1]. That means the 2028 readout may not give a simple yes-or-no answer about PCOS symptoms overall; it will address bleeding frequency and ovulation counts first [1].
Eligibility rules also limit who any eventual findings would describe. Participants must be premenopausal, between 18 and 45, with a BMI of at least 27 and a Rotterdam-criteria diagnosis, so the results would not directly describe postmenopausal women, women under 18 or over 45, or women with PCOS below that BMI threshold [1].
The trial is being run in Germany, so enrollment is not open to patients in the United States [1].
What happens next
Enrollment began December 9, 2025 [1]. With 20 weeks of dose escalation and 52 weeks of maintenance, each participant is in treatment for about a year and a half [1]. The record lists primary completion — the point at which the last participant finishes the main outcome measures — as December 2028 [1]. No interim results, publication date or conference presentation date has been disclosed [1].
Whether tirzepatide reaches the maximum tolerated dose in most participants, and how well the weekly progesterone testing captures ovulation over 52 weeks, will not be known until the trial reports [1].
Sources
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