The Protein Bound Iodine test may be used to measure the amount of thyroxin present
in the blood.
c. Diseases Involving the Thyroid Gland. There are several diseases
involving the thyroid gland.
(1) Goiter. Goiter is an abnormal enlargement of the thyroid gland
producing a distinct swelling at the base of the neck just below the larynx ("Adam's
Apple"). Simple goiters result from a dietary lack of iodine. This occurs most commonly
in areas in which the soil is relatively free of iodine and where no seafood, material high
in iodine content-is eaten. The thyroid gland, because of the lack of iodine, does not
produce enough active thyroxin. Because of this lack of thyroxin, increased amounts of
thyroid-stimulating hormone are produced, stimulating the thyroid and causing it to
increase in size. Hence, a goiter (abnormal enlargement) is formed.
(2) Graves' disease. Another form of goiter is called Graves' Disease.
Graves' Disease is the result of an overactivity of the thyroid (or hyperthyroidism). It is
also called exophthalmic goiter because of the protruding eyeballs that are
characteristic of the disease. Other symptoms associated with Graves' Disease include
nervous tension, fatigue, fast and irregular heart beat, and eventually, congestive heart
failure. The cause of Graves' disease is unknown. The result of Graves' disease is an
enlarged and hyperactive thyroid gland. Graves' disease is treated by the use of
antithyroid drugs and/or surgical removal of part of the thyroid gland. Many of the
clinical signs and symptoms typical of Graves' Disease may also be seen in patients
who take an overdose of a thyroid drug.
(3) Cretinism. Diseases involving thyroid underactivity may be seen in
children and adults. Hyposecretion of thyroxin in the fetus or newborn produces a
disease called cretinism. This lack of thyroxin causes retardation of skeletal and
nervous system growth. Untreated, this hyposecretion of thyroxin in a newborn can
result in a mentally retarded dwarf. If the disease is detected very early, the child can
be given thyroxin replacement therapy so development can be normal. Lack of thyroxin
in adults may produce myxedema. Characteristics of myxedema include edema,
fatigue, lethargy, sensitivity to cold, and other degenerative changes. The disease
reaches its peak of severity in a hypothermic coma, in which the patient goes into a
coma and the body temperature decreases to between 80 to 90 degrees Fahrenheit.
THE PARATHYROID GLANDS
The parathyroid glands are usually four in number. They are embedded in the
posterior portion of the thyroid. Their principal action is the production of parathormone.
a. Parathormone. Parathormone is a hormone that works in conjunction with
another hormone, calcitonin, to regulate the calcium and phosphate in the body. The
storehouse of calcium in the body is bone. That is, bone is being formed and
reabsorbed at the same time. Parathormone acts on bone by increasing bone