A Phase 1 interventional study of Micronized progesterone (oral capsules) and placebo capsule in Healthy Volunteers, Female and Progesterone, sponsored by McMaster University. Completed at 1 site in Canada. Open to female participants aged 18 Years to 30 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-06-17.
Sponsored by McMaster University · Phase 1, Interventional, and Basic science
The goal of this clinical trial is to learn if micronized progesterone (PROMETRIUM®) influences the muscle-building response to resistance exercise in healthy premenopausal women aged 18-30 years.
The main questions it aims to answer are:
Researchers will compare micronized progesterone to a placebo to see if progesterone changes the way skeletal muscle adapts to resistance exercise.
Participants will:
This is a single-site, randomized, double-blind, placebo-controlled Phase 1 clinical trial designed to evaluate the effects of micronized progesterone on exercise-induced skeletal muscle protein synthesis (MPS) in premenopausal women.
Participants will be healthy, naturally menstruating women aged 18-30 years. Each will be randomized to receive either two oral doses of micronized progesterone (400 mg total, administered as 2 × 200 mg capsules, 34 and 10 hours prior to testing) or a matched placebo.
During the infusion trial, participants will consume a standardized nutritional drink (\~530 kcal; 22 g protein, 52 g carbohydrate, 26 g fat) and perform unilateral resistance exercise consisting of single-leg extensions (1 warm-up set followed by 4 working sets to volitional failure, 2-minute rest between sets).
To assess myofibrillar MPS, participants will undergo a primed continuous infusion of L-[ring-¹³C₆]-phenylalanine, with incorporation into muscle proteins determined from serial biopsies collected from both the exercised and rested legs. Blood samples will be obtained throughout the infusion period to measure plasma amino acids and hormone concentrations.
The primary endpoint is the treatment (placebo vs. progesterone) × leg (exercised vs. rested) interaction in MPS over the 5-hour post-exercise period. Secondary outcomes include the exercise-induced change in fractional synthetic rate (ΔFSR), plasma hormone responses, and exploratory measures of body composition and strength.
This study will provide direct evidence on whether progesterone modifies the acute anabolic response to resistance exercise in reproductive-age women, addressing an important gap in female skeletal muscle physiology.
McMaster University is the lead sponsor of 720 studies on the registry; 124 are open to participants now.
Of its 6 completed or terminated interventional studies of FDA-regulated products, 2 (33%) have results posted.
Counted across the registry records on this site, refreshed daily.
Exclusion Criteria:
History or presence of contraindications to progesterone therapy, including any of the following:
Drug - Micronized progesterone (oral capsules; 400 mg total as 2 × 200 mg at \~34 h and \~10 h pre-trial)
Drug: Micronized progesterone (oral capsules)
Drug - Placebo (oral capsules; matched schedule and appearance)
Drug: placebo capsule
Two doses of 400 mg total micronized progesterone, administered as 2 × 200 mg capsules \~34 hours and \~10 hours prior to infusion trial, taken with a standardized nutritional drink.
Also known as: PROMETRIUM
Matched oral placebo capsules administered on the same schedule (\~34 and \~10 hours prior to infusion trial) with a standardized nutritional drink.
Myofibrillar muscle protein synthesis (MPS) rate
Incorporation of L-\[ring-¹³C₆\]-phenylalanine into myofibrillar proteins, measured via bilateral muscle biopsies (vastus lateralis, exercised vs. rested legs). The primary endpoint is the treatment (micronized progesterone vs. placebo) × leg (exercised vs. rested) interaction in MPS under fed conditions.
Time frame: 5 hours after standardized feeding and unilateral resistance exercise (infusion period)
Myofibrillar MPS in rested leg (fed condition)
MPS in the rested (non-exercised) leg to assess whether progesterone alters postprandial muscle anabolism in the absence of exercise.
Time frame: 5 hours after standardized feeding
Myofibrillar MPS in rested leg (fasted condition)
MPS calculated from baseline fasted blood/plasma enrichment and pre-meal biopsy to determine whether progesterone alters basal, fasted-state anabolism.
Time frame: -240 to 0 minutes before feeding (fasted infusion period)
Circulating serum progesterone concentrations (pharmacokinetics)
Serial serum progesterone measured to characterize exposure; pharmacokinetic parameters include AUC, Cavg, Cmax, and Tmax.
Time frame: -240 to 300 minutes (fasted and fed infusion periods)
Postprandial amino acid response
Serial serum amino acid concentrations (including essential and branched-chain amino acids) measured for PK parameters (AUC, Cavg, Cmax, Tmax) to contextualize MPS responses.
Time frame: 0 to 300 minutes after standardized feeding
Plasma tracer enrichment verification
Plasma enrichment of L-\[ring-¹³C₆\]-phenylalanine at steady-state timepoints to confirm validity of MPS calculations (target ≥2.0%).
Time frame: Throughout infusion (-240 to 300 minutes)
Baseline menstrual phase and hormonal status
Baseline serum estradiol, LH, and FSH concentrations to verify early follicular phase timing and ensure group comparability.
Time frame: Pre-dose (-240 minutes)
Plan to share: No — Individual participant data (IPD) will not be shared due to the small sample size, the invasive nature of muscle biopsy procedures, and the risk of re-identification. Results will be disseminated in aggregate form through peer-reviewed publications and scientific presentations.
No publications or documents are linked to this record.
This study is completed, as verified in Jun 2026. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
McMaster University