a. Anterior Lobe (Adenohypophysis). The anterior lobe of the pituitary gland
produces many hormones, each of which has a specific action on other endocrine
glands, including the gonads, thyroid, and adrenal cortex. For this reason, the anterior
lobe of the pituitary gland is sometimes called the master gland of the endocrine
system. By this means, hormones of the anterior pituitary lobe control the function of
other endocrine glands and influence the effects of their secretions.
b. Posterior Lobe (Neurohypophysis). The posterior lobe only stores
hormones, one of these helps to control the excretion of water from the body; another
stimulates smooth muscle contraction. Several other hormones are known to exist
249. HORMONES OF THE ANTERIOR PITUITARY
a. Somatotropin. Somatotropin (Growth Hormone) (GH or STH) causes growth
of all tissues of the body that are capable of growing. This hormone causes both
increased size of the cell itself and increased mitosis, with the development of increased
numbers of cells. This hormone increases the rate of protein synthesis in all the cells of
the body, decreases the rate of carbohydrate utilization, and increases the mobilization
of fats and the use of fats for energy.
b. Corticotropin . Corticotropin (Adrenocorticotropin, ACTH) stimulates the
adrenal cortex. ACTH causes the adrenal cortex to produce an increased quantity of
hormones. ACTH also controls the adrenal cortex to the extent that if the pituitary gland
is removed, the adrenal cortex atrophies and becomes degenerate. If fresh pituitary
gland is introduced, the adrenal cortex repairs itself.
(1) Stimulates thyroxine activity. Thyrotropin (TSH) increases the rate at
which inorganic iodine is taken up by the thyroid cells from the blood. Thyrotropin
further increases the rate at which thyroxine in the thyroid is released into the blood.
(2) Stimulates thyroid growth. Thyrotropin causes an increase in the size of
the thyroid cells and also an increase in the number of cells.
d. Follicle-Stimulating Hormone
(1) Graafian follicle control. In the female, follicle-stimulating hormone(FSH)
causes the proliferation of the ovarian follicular cells during growth of the Graafian
follicles. These cells are also stimulated to secrete small amounts of estrogen.
(2) Induction of spermatogenesis. In the male, FSH stimulates
spermatogenesis (the production of sperm).