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.Summary for lay readersThe corpus luteum is formed from the ovulated follicle under the influence of the endogenous LH surge. LH is the principal hormone that stimulates the production of progesterone and supports corpus luteum function in women. If conception fails, regression of corpus luteum takes place, a process named luteolysis. The causes of luteolysis in humans are not known. Nevertheless, the function of the corpus luteum is rescued when conception occurs by human chorionic gonadotrophin. In IVF programmes, ovarian stimulation leads to a marked suppression of LH secretion that disrupts corpus luteum function.