STEROID HORMONES

Steroids are substances derived from cholesterol. Steroid hormones control sexual maturation, sexual cycles, mating seasons, and insect metamorphosis. Primary sexual characteristics: those which are absolutely necessary for reproduction, like a uterus or egg production. Secondary sexual characteristics: those which may help attract a mate but which are not absolutely necessary for reproduction, like deep voices, beards, antlers, or peacock feathers. Seasonal variation: In animals that mate seasonally, the seasonal production of sex hormones controls the maturation and regression of sexual characteristics and sexual behavior. Androgens (masculinizing hormones): Testosterone (secreted by testes) causes development of male primary and secondary sexual characteristics. Androgens produced by the adrenal cortex produce male secondary sexual characteristics only. Estrogens (feminizing hormones), secreted by the ovaries, cause the development of both primary and secondary female characteristics. Progesterone: female hormone secreted by the ovaries after ovulation Adrenal cortex hormones: Outermost layer produces glucocorticoids, affecting some aspects of carbohydrate metabolism. Middle layer produces mineralocorticoids such as aldosterone, controlling metabolism of Na+ and other ions. Inner layer produces androgenic hormones.

rev. June 2015