[Release of estrogen-induced positive feedback in the follicular phase]

Influence of estradiol on the secretion of pituitary gonadotropins in a sense of positive feedback in formating not until the progress of development of puberty. Appearance of positive feedback mechanism, which cause the secretion of LH and FSH reason of increasing estrogen doses, induces menstrual cycle. In 10 healthy, normally menstruating women plasma LH and FSH have been measured before and every 12 hours after an intramuscular injection of 50 micrograms estradiol benzoate per kg body weight. A positive feedback could be observed between the 5th and 14th day of the menstrual cycle. At first the LH-concentration decreased and then after 36-48 hours estradiol benzoate injection induced an increase of LH.