The thyroid
gland belongs to the "ductless" or
endocrine class of glands. The thyroid
gland actually contains 2 glands in
one: the majority of the thyroid
produces thyroid hormone; small cells
scattered throughout the gland secrete calcitonin. The thyroid gland secretes
these hormones directly into the
bloodstream.
The stimulus to
secrete thyroid hormone into the blood
comes from thyroid stimulating hormone (TSH),
which is produced in the pituitary
gland. The stimulus for TSH production
comes from thyrotropin, which is
produced in the hypothalamus. Thyroid
hormone levels regulate the secretion of
thyrotropin from the hypothalamus. This
regulation creates a feedback loop. The
collection of hypothalamus, pituitary
gland and thyroid gland create an axis,
called the hypothalamic-pituitary axis (HPA).
Thyroid hormone
controls metabolism in the body. Lack
of thyroid hormone production results in
the condition of hypothyroidism.
The symptoms of which include wieght
gain, sluggishness, depression, loss of
hair, diminished reflexes, intolerance
of cold environment and so forth.
Overproduction of thyroid hormone
results in hyperthyroidism.
Symptoms of hyperthyroidism include
weight loss, fast heart rate,
nervousness or anxiety, sweating, and
intolerance of hot climate. Since
thyroid hormone affects every organ
system in the body, the symptoms of
thyroid disease are far reaching. The
listing above is not meant to be
all-inclusive.
Tests that
measure thyroid hormone and TSH levels
are used to determine the type of
thyroid disorder present. Medications
can be prescribed to help regulate
either hypo- or hyperthyroidism.
Calcitonin, the
other hormone produced in the thyroid
gland, lowers calcium levels. Its
antagonist is parathyroid hormone, which
is produced in the parathyroid glands.
You can find out more about these
hormones and the
parathyroid glands
in their web page.
There are a
multitude of diseases that produce
changes in thyroid functioning,
including Graves' disease, Hashimoto's
thyroiditis, etc. In our practice,
these patients are managed in
consultation with an endocrinologist.
