Endocrinology. A general term for a class of female sex hormones, which play an important role in the development of the female secondary sex characteristics, in the menstrual cycle, and in pregnancy. Estrogens are synthesized in the ovary and in the placenta. In men, small amounts of estrogens are produced in the adrenal cortex and in the testicles. Estrogens comprise the three hormones estradiol, estriol and estron. Their synthesis is regulated by FSH and LH, two hormones secreted by the pituitary gland.