They promote growth and development of the vagina, uterus, and fallopian tubes, and enlargement of the breasts. Indirectly, they contribute to the shaping of the skeleton, maintenance of tone and elasticity of urogenital structures, changes in the epiphyses of the long bones that allow for the pubertal growth spurt and its termination, growth of axillary and pubic hair, and pigmentation of the nipples and genitals. Decline of estrogenic activity at the end of the menstrual cycle can bring on menstruation, although the cessation of progesterone secretion is the most important factor in the mature ovulatory cycle. However, in the preovulatory or nonovulatory cycle, estrogen is the primary determinant in the onset of menstruation.
Estrogens also affect the release of pituitary gonadotropins.
The pharmacologic effects of conjugated estrogens are similar to those of endogenous estrogens. The tablets are soluble in water and are well absorbed from the gastrointestinal tract. The injection is soluble in water and may be administered by intravenous or intramuscular injection. The cream is soluble in water and may be absorbed from mucosal surfaces after local administration. As a result of estrogen action, specific RNA and protein synthesis occurs.