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Reproductive systemComments

Reproductive system

Sex organs not only produce gametes but also secrete sex hormones. Sex hormone secretion is controlled by the pituitary gland hormones such as FSH and LH. While both sexes make some of each of the hormones, typically male testes secrete primarily androgens including testosterone. Female ovaries make estrogen and progesterone in varying amounts depending on where in her cycle a woman is. In a pregnant woman, the baby's placenta also secretes hormones to maintain the pregnancy.

Oral contraceptives contain synthetic steroids that inhibit release of GnRH and then of FSH and LH, so no egg is released. However, the estrogen and progesterone in the pill supports the uterine cycle; suspension of the pill each month permits menstruation. Two new hypothalamic peptides work in opposition to control: Gonadotropin-inhibiting hormone (GnIH) inhibits and kisspeptin stimulates GnRH secretion.