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There are two fairly
common causes of hypothyroidism
The
first is a result of previous (or currently
ongoing) inflammation of the thyroid gland
which leaves a large percentage of the cells of
the thyroid damaged (or dead) and incapable of
producing sufficient hormone. The most common
cause of thyroid gland failure is called
autoimmune thyroiditis (also called Hashimoto's
thyroiditis), a form of thyroid inflammation
caused by the patient's own immune system.
The second major cause is the broad category of
"medical treatments". As noted on a number
of our other pages, the treatment of many
thyroid conditions warrants surgical removal of
a portion or all of the thyroid gland. If the
total mass of thyroid producing cells left
within the body are not enough to meet the needs
of the body, the patient will develop
hypothyroidism. Remember, this is often the goal
of the surgery as seen in surgery for thyroid
cancer. But at other times, the surgery will be
to remove a worrisome nodule, leaving half of
the thyroid in the neck undisturbed. Sometimes
(often), this remaining thyroid lobe and isthmus
will produce enough hormone to meet the demands
of the body. For other patients, however, it may
become apparent years later that the remaining
thyroid just can't quite keep up with demand.
Similarly, goiters and some other thyroid
conditions can be treated with radioactive
iodine therapy. The aim of the radioactive
iodine therapy (for benign conditions) is to
kill a portion of the thyroid to
-
prevent goiters from growing larger, or
-
producing too much hormone
(hyperthyroidism).
Occasionally, (often?) the result of radioactive
iodine treatment will be that too many cells are
damaged so the patient often becomes hypothyroid
a year or two later. This is O.K. and usually
greatly preferred over the original problem.
There are several other rare causes of
hypothyroidism, one of them being a completely
"normal" thyroid gland which is not making
enough hormone because of a problem in the
pituitary gland. If the pituitary does not
produce enough Thyroid Stimulating Hormone (TSH)
then the thyroid simply does not have the
"signal" to make hormone, so it doesn't. |
