Menstrual cycle and the lining of the uterus thickens. Follicles in the ovary begin developing under the influence of a complex interplay of hormones, and after several days one or occasionally two become dominant (non-dominant follicles shrink and die). Approximately mid-cycle, 24–36 hours after the luteinizing hormone (LH) surges, the dominant follicle releases an ovocyte, in an event called ovulation. After ovulation, the ovocyte only lives for 24 hours or less without fertilization while the remains of the dominant follicle in the ovary become a corpus luteum; this body has a primary function of producing large amounts of progesterone. Under the influence
Pharmacokinetics of progesterone half-life of progesterone in the circulation is very short at a range of about 3 to 90 minutes. Previous studies using RIA have reported an overestimated half-life of oral progesterone of about 16 to 18 hours. A subsequent, reliable study using high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) reported a half-life of oral progesterone of about 4.6 to 5.2 hours when it was taken with food. Due to the short half-life and duration of action of oral progesterone, it is often taken in divided doses of two or three times per day. Because of studies that used RIA, it was incorrectly