Thyroid Gland Central Dysfunction
(continued)
Hypothyroidism results when the thyroid produces an insufficient amount
of thyroid hormone. It affects 11 million Americans and is the most common form
of thyroid disease; it is more than four times as prevalent as hyperthyroidism.
Whereas hyperthyroidism is most common in younger women, hypothyroidism generally
affects women in their 50's to 60's: by age 60, one in 6 women will have an
under active thyroid. Even though it is much more common than hyperthyroidism,
it is much more frequently undiagnosed, however, because its symptoms are easily
attributed-by patients themselves as well as their physicians--to aging, menopause,
fatigue or stress. In fact, a recent survey of 1,000 women over age 40 conducted
by Louis Harris in conjunction with the American Medical Women's Association
(AMWA) found that nearly 2 out of 3 women do not know what "hypothyroidism"
means. This was despite the fact that more than half of these women experienced
three or more symptoms commonly associated with hypothyroidism over the past
year. Of those women, 3 out of 4 never discussed those symptoms with their physician.
9 out of 10 cases, hypothyroidism results from a problem in the thyroid gland
itself. The most common cause of hypothyroidism is Hashimoto's disease (or
Hashimoto's thyroiditis), a condition in which the immune system produces antibodies
that destroy the thyroid. In all types of hypothyroidism, the less thyroid hormone
produced, the more TSH released by the pituitary. This acts on the thyroid gland
to enlarge it, which may cause a "goiter". Other causes of hypothyroidism include
complications of either thyroid or parathyroid surgery, radioiodine treatments
for hyperthyroidism; or a congenital thyroid birth defect. Short-term hypothyroidism
may also be the result of certain types of thyroid inflammation or viral thyroid
infections. Goiters themselves may also be caused by a dietary insufficiency
of iodine.
Rarely, in about 1 in 20 cases, hypothyroidism may be caused by a problem in
the hypothalamus or pituitary gland rather than in the thyroid gland itself.
Under normal circumstances, the hypothalamus signals the pituitary gland to
produce TSH. When a medical problem affects either the hypothalamus or the pituitary
gland, the chain of signals from the brain to the thyroid may be interrupted.
If this happens, the thyroid gland may not receive the pituitary's message to
produce thyroid hormones, even though the thyroid itself can function perfectly.
This type of hypothyroidism, called "secondary hypothyroidism," may be caused
if the pituitary is damaged by a tumor, infection, sarcoidosis, or cancer.
Hypothyroidism in pregnancy may be a bigger problem than we previously
recognized. This affects one in 50 pregnant women. While only one in every 4,000
babies is born with clinical hypothyroidism, a recent study (8/99) in the prestigious
New England Journal of Medicine (NEJM) showed that untreated thyroid
disease in pregnant mothers may result in a child having impaired psychological
development as well as significantly decreased IQ scores, motor skills, language
skills, and reading abilities. . . even though the baby's thyroid function is
normal. Ask your doctor whether you should be screened for thyroid disease if
you are planning to become pregnant or if you are early in your current pregnancy.
It is also important to recognize that five to eight percent of women develop
thyroid disorders after giving birth.