any of the hormones that stimulate various reproductive functions. Primary sources of sex hormones are the male and female gonads (i.e., testis and ovary), which are stimulated to produce sex hormones by the follicle-stimulating hormone and luteinizing hormone secreted by the pituitary gland. The principal male sex hormones (androgens) include testosterone; female sex hormones include the estrogens, progesterone, and prolactin.