Menstrual cycle and LH cause the remaining parts of the dominant follicle to transform into the corpus luteum, which produces progesterone. The increased progesterone in the adrenals starts to induce the production of estrogen. The hormones produced by the corpus luteum also suppress production of the FSH and LH that the corpus luteum needs to maintain itself. Consequently, the level of FSH and LH fall quickly over time, and the corpus luteum subsequently atrophies. Falling levels of progesterone trigger menstruation and the beginning of the next cycle. From the time of ovulation until progesterone withdrawal has caused menstruation to begin, the process
Pharmacokinetics of progesterone 800 mg/day vaginal progesterone (about 70 ng/mL and 12 ng/mL, respectively), although local progesterone levels in the uterus were 10 times higher with the vaginal route due to a uterine first-pass effect (around 1.5 ng/mL and almost 12 ng/mL, respectively). The duration of progesterone is extended by the intramuscular route due to a depot effect in which it is stored locally in adipose tissue, and can be administered once every 1 to 3 days. The half-life of intramuscular progesterone is significantly longer when it is injected into the gluteal muscles of the buttocks rather than the deltoid muscle of the