A gonad or sex gland or reproductive gland is an endocrine gland that produces the gametes (sex cells) of an organism. In the female of the species the reproductive cells are the egg cells, and in the male the reproductive cells are the sperm. The male gonad, the testicle, produces sperm in the form of spermatozoa. The female gonad, the ovary, produces egg cells. Both of these gametes, are haploid germ cells.
The gonads are controlled by luteinizing hormone and follicle-stimulating hormone, produced and secreted by gonadotropes in the anterior pituitary gland. This secretion is regulated by gonadotropin-releasing hormone produced in the hypothalamus.
Gonads start developing as a common primordium (an organ in the earliest stage of development), in the form of gonadal ridges, and only later are differentiated to male or female sex organs. The presence of the SRY gene, located on the Y chromosome and encoding the testis determining factor, determines male sexual differentiation. In the absence of the SRY gene from the Y chromosome, the female sex (ovaries instead of testes) will develop. The development of the gonads is a part of the development of the urinary and reproductive organs.