Hormones and Antiaging Medicine: Male Hormones and Antiaging

Male hormones (androgens) include testosterone (T), which is mainly produced in the Leydig cells in the interstitium of the testes, and dehydroepiandrosterone (DHEA) derived from the adrenal glands. T is also produced in the hippocampus, muscles, and fat. About 98% of T in the blood is bound to sex hormone-binding globulin (SHBG) and albumin, and the remaining 1–2% exists as free (unbound) T [1]. Total T includes both bound and free forms. In target tissues, T is converted to dihydrotestosterone (DHT), which has high activity, by the action of 5α-reductase. It is believed that adrenal-derived DHEA also acts by being converted to T or DHT. The androgen receptor (AR), a receptor for T and DHT, is a nuclear receptor. When it binds to T or DHT, it acts as a transcription factor for target genes, showing various biological activities. T has diurnal variations and also varies with stress and lifestyle habits. T plays many important physiological roles, including differentiation of male reproductive organs, manifestation of secondary sexual characteristics, sperm formation, and effects on muscles, bones, central nervous system, prostate, bone marrow, skin, and sexual function.