What are hormones?
Hormones are chemical messengers that are made by glands in the body. Hormones are delivered through the bloodstream and act on other organs in the body. In this section, the role of hormones controlling male reproductive function will be described and includes:
 Gonadotropin-releasing hormone (GnRH)
which is secreted by the hypothalamus that sits at the base of the brain. GnRH controls the secretion of other hormones from the pituitary gland, which is another small gland at the base of the brain. The hypothalamus also has other functions that are not related to reproductive function.
- Luteinizing hormone (LH)
which is secreted by the pituitary gland in response to a GnRH signal. LH acts on the Leydig cells in the testes. Once stimulated with LH, the Leydig cells in the testes produce testosterone.
- Follicle stimulating hormone (FSH)
is also secreted by the pituitary gland in the brain. Together with testosterone, FSH stimulates Sertoli cells (located in the seminiferous tubules of the testes) to support the developing sperm.
- Testosterone
is probably the most familiar ‘male hormone’ produced by LH-stimulated Leydig cells in the testis. Testosterone, together with FSH, is needed for normal sperm production. Of interest, females also produce testosterone but at much lower levels.
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