The gonad is the organ that makes gametes. Gametes are haploid germ cells. For example, sperm and egg cells are gametes.

In males, the gonads, known as the testes, secrete the class of hormones called androgens. The predominant androgen in males is testosterone. In females, the gonads, known as the ovaries, secrete estrogen and progesterone. The dominant estrogen is known as estradiol, which is derived from testosterone.

The gonads are controlled hormonally by luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secreted by the anterior pituitary gland. The anterior pituitary gland's excretion of LH and FSH are, in turn, controlled by the hypothalamus's gonadotropin-releasing hormone.