The pituitary is a gland found in
higher animals. It is an endocrine gland that pours its secretion
directly into the blood stream. It is located on the underside of the
brain, where it is well protected. The pituitary gland controls growth
and many other glands and organs of the body.
The pituitary, or hypophysis, is a very small egg-shaped gland of about
one centimeter in diameter and about 0.6 gram in weight. It is
frequently referred to as the "master gland," but this is not entirely
accurate since among the ductless glands of the body there is great
interdependence— that is, they influence one another. No one gland is
the key to the total system. Nonetheless the pituitary is of great
importance because it affects the functioning of several organs in the
body. Experimentation by means of injections of individual hormones
produced by the gland, as well as through removal of portions of the
gland, has given much information about it.
The pituitary may be divided into three main areas, the front part
called the anterior lobe, a narrow middle area, the intermedíate lobe,
and the rear portion or posterior lobe.
The anterior lobe produces a number of hormones. Oversecretion of one of
these brings about a condition known as gigantism. This, occurring in
young people, causes an overdevelopment and lengthening of bones. The
absence of this hormone can also bring about underdevelopment or
dwarfism. For this reason it is called a growth hormone, though there
are hormones produced by other glands which also affect growth.
Other hormones of the anterior lobe control the development and
functioning of sexual organs. Another brings about milk production.
Still others stimulate the thyroid gland (affecting growth patterns)
the adrenal cortex, and the parathyroid glands.
The posterior lobe of the pituitary produces a hormone called pituitrin, a hormone which can be divided into several fractions, each affecting certain processes of the body. Pituitrin plays an important role in childbirth, causing contractions of muscles of the uterus and assisting in bringing about the birth process. Inadequate secretion of pituitrin causes excessive urine formation, or diabetes insipidus.
