Progesterone ELISA

Enzyme immunoassay for the quantitative determination of Progesterone in human serum and plasma. Progesterone (pregn-4-ene-3, 20-dione) is a C21 steroid hormone containing a keto-group (at C-3) and a double bond between C-4 and C-5. This steroid hormone is a female sex hormone which, in conjunction with estrogens, regulates the accessory organs during the menstrual cycle and it is particularly important in preparing the endometrium for the implantation of the blastocyte and in maintaining pregnancy. In non-pregnant women progesterone is mainly secreted by the corpus luteum whereas in pregnancy the placenta becomes the major source. Minor sources are the adrenal cortex for both sexes and the testes for males. Progesterone circulates in blood mainly bound to Corticosteroid Binding Globulin (CBG), Sex Hormone Binding Globulin (SHBG) and Albumin. Only 2-10% of the total concentration circulates as free hormone. Blood progesterone concentrations vary widely according to the phases of menstrual cycle. The maximal levels are achieved 4-7 days after ovulation and remain elevated for 4-6 additional days prior to falling to the preovulatory levels 24 hours before the onset of menstruation. If ovulation does not occur the corpus luteum is not formed and no cyclical rise of progesterone in plasma is observed. Progesterone concentration can vary not only from subject to subject but also in the same person from day to day or even from hour to hour. During pregnancy progesterone is widely produced by placenta, and plasma levels rise steadily achieving high values at term.