The menstrual and ovarian cycles, and other features of human reproductive systems, depend on the endocrine glands for their regulation and control. These are glands that release their secretions, called hormones, into the extracellular fluid that surrounds the cells making up the gland. The secretion then usually passes into the capillaries, to be transported by the blood where it circulates until it reaches the target organ – the organ on which it will have an effect. The main target organs for hormones involved in reproductive processes are the testes of the male and the ovaries of the female.

One of the important endocrine glands associated with the reproductive system is the pituitary gland. The pituitary is a small organ lying in a pit in the bone below the brain and above the roof of the mouth. Some of the hormones it secretes affect parts of the reproductive system. Two hormones secreted by the pituitary affect the gonads and are thus called gonadotropic hormones, or gonadotropins.

Follicle-stimulating hormone (FSH) stimulates the development and maturation of the ovarian follicle in females. During its development, the ovarian follicle secretes its own hormone, oestrogen. Secretion of FSH is reduced as the level of oestrogen increases in the blood.

Luteinising hormone (LH) promotes the final maturation of the ovarian follicle, ovulation, and the formation of the corpus luteum. The corpus luteum secretes another ovarian hormone, progesterone, as well as oestrogens. There is a gradual reduction in the production of LH as the level of progesterone in the blood increases.

Bone In addition to the gonadotropic hormones, the pituitary gland releases prolactin and oxytocin. Prolactin has a direct effect on the breasts of the woman, and together with other hormones, is important in the preparation and maintenance of milk production. Oxytocin causes uterine contractions, promotes the movement of milk in the breast, and has a role in the movement of sperm and the production of testosterone in the testes. In males, the same gonadotropic hormones are secreted by the pituitary gland. FollicleYour hormones This website has more information about the different hormones. stimulating hormone stimulates the epithelial tissue of the seminiferous tubules in the testes to produce sperm. LH stimulates cells in the testes to secrete the hormone testosterone. Testosterone is important for the development of immature sperm cells into mature spermatozoa, and has a major role in the maintenance of the male reproductive organs and sex drive. At puberty, the secretion of gonadotropic hormones stimulates a number of changes, both physical and psychological and in both males and females. In males, the production of testosterone influences the development of the body to sexual maturity. In females, sexual maturation is brought about by oestrogens