The Effects of Oral Contraceptives on Muscle Hypertrophy.

Muscle mass is essential for both general health and athletic performance because it supports strength, functional capacity, and physical performance. Hormonal contraceptives are used by a variety of individuals, including athletes and those who exercise. Most contraceptives contain ethinyl estradiol and a progestin, hormones that may impact muscle adaptations and hypertrophy. A limited number of studies, predominantly focused on oral contraceptives, have examined the relationship between hormonal contraceptives and muscle hypertrophy, with mixed findings. This narrative review synthesizes the current literature on how oral contraceptives may affect hypertrophic responses, considering both mechanistic and applied perspectives. The evidence generally suggests that oral contraceptive use does not consistently alter muscle hypertrophy following resistance training, though a small number of studies reported significant negative effects. These findings may be attributable, in part, to the use of more androgenic progestins. However, variability in contraceptive formulation, training protocols, and cohort sizes limits direct comparisons across studies. While mechanistic studies suggest that endogenous and synthetic sex hormones influence pathways involved in skeletal muscle remodeling, clinical studies of oral contraceptive use have not consistently demonstrated clinically meaningful differences in muscle hypertrophy. We recommend well-powered studies comparing progestins with differing androgenic activity, as well as mechanistic studies on muscular growth pathways, to better understand the influence of oral contraceptives on muscle adaptation.