Table 1.

Sex hormones and their biological functions.

Sex hormones	Biological functions
Androgens
Testosterone	Development of male genitalia, increase in muscle and bone mass, growth of body hair
Dihydrotestosterone	Catalyzed from testosterone, considerably more potent agonist of the androgen receptor
Androstenedione	Precursor of testosterone, endogenous pro-hormone, weak androgenic, and estrogenic activity
Estrogens
Estrone (E1)	Weak estrogen, precursor of estradiol
Estradiol (E2)	Potent estrogenic hormone: regulation of the estrous and menstrual female reproductive cycle, development of female genitalia, bone growth and density, skin health, neuroprotective
Estriol (E3)	Weak estrogen, almost undetectable in non-pregnant women, high levels during pregnancy
Estetrol (E4)	Weak estrogen found only in pregnancy, physiological function unknown