**1.1.3 Progesterone**

Progesterone is synthesized and secreted mainly by the corpus luteum in the ovary of cycling females, and, during pregnancy, by the placenta.

As all hormones, progesterone synthesis and secretion is regulated by a series of positive and negative feedback mechanisms in which polypeptidic hormones secreted by the brain (hypothalamus, pituitary) affect circulating progesterone levels.

Progesterone and synthetic progestins are used pharmacologically in women in conjunction with ovulation stimulation drugs as well as during early pregnancy in cases of luteal phase dysfunction. Although results have been conflicting, some studies find an association between pregnancy-related intake of progestins and increased risk of hypospadias (congenital malformation of the urethral opening on the penis) in the male offspring (Carmichael *et al.,* 2005). It should however be noted that this was observed in relation to pharmacological doses of progestins, and as progesterone levels are normally high during pregnancy, minor additional exogenous progestagenic activity would presumably be without significant effects in the presence of a high endogenous activity, unless the synthetic progestins act at different sites and by different mechanisms. In contrast, serum levels of progestins in children and postmenopausal women are very low. Data on effects of progesterone in the prepubertal child are scarce and no new data have been identified. Likewise, no animal studies on the effects of progesterone during the postnatal development have been published recently.

It is well established that progesterone not only serves as the precursor of all the major steroid hormones (androgens, oestrogens, corticosteroids) in the gonads and adrenals, but also is converted into one or more metabolites by most tissues in the body (Wiebe, 2006).
