Effects of ethinyl estradiol-containing oral contraception and other factors on body composition and muscle strength among young healthy females in Finland—A cross-sectional study

The effect of sex hormones on skeletal muscle adaptation in females

Sex steroids, commonly referred to as sex hormones, are integral to the development and maintenance of the human reproductive system. In addition, male (androgens) and female (estrogens and progestogens) sex hormones promote the development of secondary sex characteristics by targeting a range of other tissues, including skeletal muscle. The role of androgens on skeletal muscle mass, function and metabolism has been well described in males, yet female specific studies are scarce in the literature. This narrative review summarises the available evidence around the mechanistic role of androgens, estrogens and progestogens in female skeletal muscle. An analysis of the literature indicates that sex steroids play important roles in the regulation of female skeletal muscle mass and function. The free fractions of testosterone and progesterone in serum were consistently associated with the regulation of muscle mass, while estrogens may be primarily involved in mediating the muscle contractile function in conjunction with other sex hormones. Muscle strength was however not directly associated with any hormone in isolation when at physiological concentrations. Importantly, recent evidence suggests that intramuscular sex hormone concentrations may be more strongly associated with muscle size and function than circulating forms, providing interesting opportunities for future research. By combining cross-sectional, interventional and mechanical studies, this review aims to provide a broad, multidisciplinary picture of the current knowledge of the effects of sex steroids on skeletal muscle in females, with a focus on the regulation of muscle size and function and an insight into their clinical implications. HighlightsFree testosterone, but not total testosterone, is associated with lean mass but not strength in pre- and post-menopausal females.Progesterone and estrogens may regulate muscle mass and strength, respectively, in females.Intra-muscular steroids may be more closely associated to muscle mass and strength, compared to systemic fractions.

Regulatory aspects of myogenic factors GDF-8 and Follistatin on the intake of combined oral contraceptives

Combined oral contraceptives are one of the most prescribed drugs in the western world. While there is little evidence regarding effects of estrogen or gestagens on muscle metabolism, androgens are well-known for their anabolic characteristics. In this study, we seeked to investigate potential correlations of the myokines GDF-8, IGF-1 and Follistatin with female sexual hormones and likewise possible interactions with combined oral contraceptives (Dienogest and Ethyl Estradiol) intake. We obtained serum samples of young healthy women to measure hormone correlations. Furthermore, we simulated combined oral contraceptive blood circulating hormone concentrations to identify myogenic effects on HSkM in vitro. GDF-8, IGF-1 and Follistatin showed concentration correlations (p = .005) in overall patients' serum, while Follistatin as a promyogenic protein additionally showed a positive correlation with testosterone and estradiol (p < .05). Lower GDF-8 levels were also linked to a higher BMI (p = .009). Upon combined oral contraceptives (COC) intake, patients showed decreased GDF-8 (p = .006) but increased Follistatin (p = .0001) concentrations compared to patients without COC intake. In vitro, addition of Ethyl Estradiol and Dienogest to HSkM cells revealed a pro-myogenic, proliferative, chemosensitized pattern. Our data support a pro-myogenic effect of combined oral contraceptives.