Myofibrillar Protein Synthesis Rates Do not Differ With Low and High Estradiol Concentrations Across the Menstrual Cycle
Authors' conclusion
Despite a gene expression profile consistent with muscle growth, MyoPS did not differ with elevated estradiol concentrations. Hence, estradiol does not seem to be important for acutely regulating muscle mass in eumenorrheic women.
Study context
- Population
- Healthy women (age 28 ± 7 y; BMI 24 ± 3 kg.m²); resistance exercise bout followed by amino acid drink
- Participants
- 17 women
- Comparison
- Early follicular vs late follicular phase of the menstrual cycle
- Primary endpoint
- MyoPS in postabsorptive and postprandial postexercise states
- Follow-up
- 4 hour postprandial postexercise period
Methodological detailsrandomized, Primed-continuous infusion of L-[ring-2H5]-phenylalanine; blood and muscle samples pre and post exercise and amino acid (AA) ingestion
- Randomized
- Primed-continuous infusion of L-[ring-2H5]-phenylalanine; blood and muscle samples pre and post exercise and AA ingestion
Primary result
As reported in the abstract
0-2 hours
P = 0.971 for interaction
- Myofibrillar protein synthesis (MyoPS) increased above postabsorptive rates between 0-2 hours
- P < 0.001
- MyoPS not increased between 2-4 hours
- P = 0.522
Further findings
Correlation of testosterone with 0-4 hour MyoPS
- Total testosterone
- r = 0.364, P = .048
- Free testosterone
- r = 0.369, P = .045
- Moderate correlations
Muscle gene expression
- Genes for protein synthesis, muscle remodeling and inflammation increased in late follicular (LF) vs early follicular (EF)
- P < 0.050
- Protein breakdown genes decreased in LF vs EF
Original publication
Myofibrillar Protein Synthesis Rates Do not Differ With Low and High Estradiol Concentrations Across the Menstrual Cycle. J Clin Endocrinol Metab. Published 18 July 2025. doi:10.
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