NCT07173361

Progesterone and Muscle Protein Synthesis in Premenopausal Women (MP4-MPS)

Investigating the Impact of Micronized Progesterone on Skeletal Muscle Metabolism

• Status: Not Yet Recruiting
• Phase: Phase 1
• Study type: Interventional
• Enrollment: 20 (estimated)
• Sponsor: McMaster University · Academic / Other
• Sex: Female
• Age: 18 Years – 30 Years
• Healthy volunteers: Accepted

Summary

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: 1. Does progesterone change the rate of muscle protein synthesis after exercise? 2. Does progesterone alter the difference in synthesis between an exercised leg and a rested leg? Researchers will compare micronized progesterone to a placebo to see if progesterone changes the way skeletal muscle adapts to resistance exercise. Participants will: * Take two oral doses of progesterone (400 mg total, 34 and 10 hours before testing) or placebo * Complete a unilateral leg extension exercise session in the lab * Receive an infusion of a stable isotope tracer and provide blood samples * Undergo muscle biopsies from the exercised and rested legs

Detailed description

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.

Conditions

• Healthy Volunteers
• Female
• Progesterone
• Premenopausal

Interventions

Type	Name	Description
DRUG	Micronized progesterone (oral capsules)	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.
DRUG	placebo capsule	Matched oral placebo capsules administered on the same schedule (\~34 and \~10 hours prior to infusion trial) with a standardized nutritional drink.

Timeline

• Start date: 2025-09-15
• Primary completion: 2025-12-15
• Completion: 2025-12-15
• First posted: 2025-09-15
• Last updated: 2025-09-25

Locations

1 site across 1 country: Canada