Section II. ENDOCRINE GLANDS
In order to gain an understanding of some of the drugs that will be presented
later in the subcourse, you must become familiar with the endocrine glands and the
functions they perform. As you read the paragraphs below, associate the gland with the
substance(s) it produces and with the function(s) performed by the/those substance(s).
THE PITUITARY BODY
a. Location. The pituitary body is a small pea-sized and pea-shaped structure.
It is attached to the base of the brain in the region of the hypothalamus. In addition, it is
housed within a hollow of the bony floor of the cranial cavity. The hollow is called the
sella trucica ("Turk's saddle"). This gland is sometimes referred to as the "master
gland" of the body because of the many effects it produces.
b. Major Subdivisions of the Pituitary Body. The pituitary body is actually
two glands, the posterior pituitary gland and the anterior pituitary gland. Initially
separate, these glands join together during development of the embryo.
THE POSTERIOR PITUITARY GLAND
The posterior pituitary gland is the portion that comes from and retains a direct
connection with the base of the brain. The hormones of the posterior pituitary gland are
actually produced in the hypothalamus of the brain. From the hypothalamus, the
hormones are delivered to the posterior pituitary gland where they are released into the
bloodstream. At present, we recognize two hormones of the posterior pituitary gland.
a. The Antidiuretic Hormone. The Antidiuretic Hormone (ADH, Vasopressin) is
involved with the resorption or salvaging of water within the kidneys. Therefore, this
hormone produces its main effects in the kidneys. In the kidney, ADH increases the
permeability of the distal tubules collecting tubules, thus causing the antidiuretic effect
by osmosis. In large doses, vasopressin increases blood pressure by direct stimulation
of the smooth muscles in the vessels. This effect is seen only with injections of
vasopressin. Diabetes insipidus is a disorder that may be caused by hyposecretion of
vasopressin. Diabetes insipidus is characterized by polyuria (excessive urine
production). As much as 20 to 40 liters of urine may be excreted in one day by a patient
who has diabetes insipidus. Polydipsia (excessive thirst) is another characteristic of
b. Oxytocin. Oxytocin is a hormone concerned with contractions of smooth
muscle in the uterus and with milk secretion. The contractions occur in the pregnant
female. Milk secretion is an effect of oxytocin that occurs after the female has delivered