Luteal-phase endocrinology.

The corpus luteum is formed from the pre-ovulatory follicle under the action of the mid-cycle LH surge. LH is the main luteotrophic hormone in women controlling luteal structure and function during the normal menstrual cycle. Local factors, however, including progesterone are also involved. If conception does not take place, luteolysis occurs as a physiological apoptotic process. Human chorionic gonadotrophin, secreted after implantation, is able to rescue the corpus luteum and extend its lifespan. In ovulation-induction cycles, the negative feedback effect of the ovarian steroids on the pituitary is markedly potentiated, leading to the suppression of endogenous LH secretion during the whole menstrual cycle. The marked suppression of LH secretion disrupts corpus luteum function regardless of the treatment regimen.