Steroid hormones are natural hormones produced in the adrenal glands, testes, and ovaries (and in the placenta during pregnancy). There are five major classes of steroid hormones that are derived from the same cholesterol precursor: 1) androgens, 2) estrogens, 3) progestins, 4) mineralcorticoids, and 5) glucocorticoids. Androgens and estrogens function in sexual development, differentiation, and the development of secondary sex characteristics and behaviors. Progestins act to regulate the menstrual cycle and pregnancy. Mineralcorticoids and glucocorticoids do not have established functions in reproduction but do influence a wide variety of vital biological functions.