b. Hormones. Scientists are not sure of the effect of the hormones secreted by
the pineal gland. It is known that this gland causes animals to come into heat.
Research indicates the following in regard to humans:
(1) Melatonin. This hormone seems to be secreted on a day/night cycle
with the highest production at night and the lowest production during the day. Its
function is to prevent ovarian secretion.
(2) Serotonin. This hormone seems to prevent extremes in the blood
vessels of the brain. If blood vessels in the brain seem too small, serotonin dilates the
vessels (makes them wider). The levels of this hormone are highest at noon and lowest
Glomerulotropin. This hormone stimulates the secretion of adrenal
a. Description. The pituitary gland is small weighing only about 600 mg;
however, it is a key organ. The pituitary gland influences every structure and system in
the body. Structurally and functionally, the pituitary gland is divided into two lobes: the
anterior lobe and the posterior lobe.
b. Anterior Lobe--Hormones.
(1) Adrenocorticotropic hormone (ACTH). This hormone is secreted by the
anterior lobe of the pituitary gland. ACTH stimulates the adrenal cortex to produce
steroid hormones. A primary action of ACTH is to promote and maintain normal growth
and development of the adrenal cortex.
(2) Follicle-stimulating hormone (FSH). FSH stimulates the normal growth
cycle of the ovarian follicle in females. In males FSH stimulates the seminiferous
tubules (tubes that convey semen) to produce spermatozoa.
(3) Growth hormone (GH). This hormone promotes fat mobilization,
prevents glucose from being used, and affects the rate of skeletal and visceral (internal
organs) growth. Too much of this hormone can cause diabetes. Also, an excess of this
hormone in early life can cause a child to become a giant. Too little of this hormone is
early life can cause an infant to become a dwarf. Another name for GH is somatotropin.
(4) Interstitial cell stimulating hormone (ICSH). ICSH stimulates testicular
interstitial cells in the male to produce androgen, a substance that stimulates the
development of male sex characteristics. This hormone in the male is the same as the
luteinizing hormone in the female which is essential for ovulation (discharge of an ovum
from the mature follicle of the ovary).