Gonads

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Biological: Behavioural genetics · Evolutionary psychology · Neuroanatomy · Neurochemistry · Neuroendocrinology · Neuroscience · Psychoneuroimmunology · Physiological Psychology · Psychopharmacology (Index, Outline)

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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.

Although it can refer to testicles or ovaries when used in a medical context, the slang use of "gonads" (or "nads") usually only refers to testicles. The usage of such is similar to "balls."

Gonads start developing as a common anlage, and only later are differentiated to male or female sex organs. The SRY gene, located on the Y chromosome and encoding the testis determining factor, decides the direction of this differentiation.