Exercise and sex steroid hormones in skeletal muscle.

Sex steroid hormones are secreted mainly by the ovary and testis and regulate diverse physiological processes in target tissues. Recent studies have shown that sex steroidogenesis-related mRNA and protein expressions, such as for 17β-hydroxysteroid dehydrogenase (HSD), 3β-HSD, 5α-reductase and aromatase cytochrome P-450 (P450arom) enzymes, are detected in the skeletal muscle, while testosterone, estradiol, and 5α-dihydrotestosterone (DHT) were locally synthesized in skeletal muscle from dehydroepiandrosterone (DHEA). Moreover, in animal and human studies, the sex steroidogenesis enzymes and sex steroid hormone levels in skeletal muscle are upregulated by acute and chronic exercise stimulation. The enhanced muscle sex steroidgenesis is associated with glycemic control via upregulation of muscle glucose transporter-4 (GLUT-4) signaling in obese and diabetic rats and with muscle mass and strength in older men. Thus, an exercise-induced increase of sex steroid hormone in muscle may positively impact age-related concerns such as life-related diseases and sarcopenia.