Functions of Progesterone
of Progesterone on the Uterus. By far the mostimportant function of
progesterone is to promotesecretory
changes in the uterine endometrium duringthe latter half of the monthly
female sexual cycle, thus preparing the uterus for implantation of the
fertilized ovum. This function is discussed later in connection with the
endometrial cycle of the uterus.
In addition to this effect on the endometrium, progesterone decreases
the frequency and intensity of uterine contractions, thereby helping to prevent
expulsion of the implanted ovum.
of Progesterone on the Fallopian Tubes. Progesteronealso promotes increased secretion
by the mucosal lining of the fallopian tubes. These secretions are necessary
for nutrition of the fertilized, dividing ovum as it traverses the fallopian
tube before implantation.
of Progesterone on the Breasts. Progesteronepromotes development of the lobules
and alveoli of the breasts, causing the alveolar cells to proliferate, enlarge,
and become secretory in nature. However, progesterone does not cause the
alveoli to secrete milk; milk is secreted only after the prepared breast is
further stimulated by pro-lactin from
the anterior pituitary gland.
Progesterone also causes the breasts to swell. Part of this
swelling is due to the secretory development in the lobules and alveoli, but
part also results from increased fluid in the subcutaneous tissue.