Description
Progesterone, a C21-steroid, is a female sex hormone and a precursor in the metabolism of other steroids.
Progesterone is synthesized mainly in the corpus luteum of the ovaries, during the main part of pregnancy in the placenta and in very small amounts for the production of other steroids in the adrenal cortex and in the testes. At the latter locations, progesterone is important for the synthesis of aldosterone, cortisol, testosterone and 17β-estradiol. In the circulation, the main part of progesterone is bound to the corticoid binding globulin (CBG, Transcortin), to the sex hormone binding globulin (SHBG) and to albumin. 1 – 2 % of progesterone circulates as a free hormone in plasma. Only this portion represents the active part in the endocrine regulation. The free hormone is released in equal amounts in saliva. An enzymatic metabolization of portions of this hormone in the saliva glands is presumed.
Progesterone is an important hormone of the endocrine regulation of the menstrual cycle.
After ovulation, progesterone is secreted by the corpus luteum which develops from the ovulated follicle in the ovaries. The progesterone level rises in the 6th – 8th day after ovulation to a plateau. Together with estradiol it inhibits the release of LH and FSH in the pituitary gland by a negative feedback mechanism. Progesterone is secreted into the circulation in a pulsating way. Because of the lysis of the corpus luteum, the progesterone level decreases in the last 3 days of the cycle to a pre-ovulatory level. In pregnancy, beginning at the 8th gestation week, the placenta becomes the major source of progesterone production during the 2nd and 3rd trimester. The course of progesterone levels in the circulation is reflected in its concentration in saliva. The most important task of progesterone is to prepare the genital organs of the women for a potential implantation and to maintain the pregnancy. The main effects of progesterone are to introduce the secretory phase of the endometrium, to suppress the contractions of the uterus and to stimulate the growth of mammary tissue, as well as other effects on the metabolism and the endocrine system in women. The measurement of progesterone in saliva is useful in monitoring the menstrual cycle in women in order to determine the time of ovulation and to assess the function of the corpus luteum, which becomes important in the early stages of pregnancy.
The IBL SaliCap Set is used for the collection, handling, and storage of saliva used in the Progesterone Luminescence Immunoassay.