Estrogens, progestins and hormonal contraceptives
The two principal female hormones are estradiol and progesterone. Their secretion varies according to age: low during infancy it increases at puberty and decreases at the menopause. During the reproductive life they present cyclic variations over 28 days, plasma concentrations of estradiol, progesterone, testosterone, FSH and LH vary during the menstrual cycle.
The ovary contains primordial follicles. From puberty, each month, under the influence of FSH and LH, approximately 20 of these follicles enter development, but only one of them achieves its maturation through to the expulsion of the ovum. After expulsion of the ovum, the follicle is transformed into the corpus luteum which secretes progesterone to prepare the uterus for nidation. In the absence of fecundation, the corpus luteum regresses.