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Older women who receive too much thyroid
replacement hormone or who have a history of overactive thyroid
may face a greater risk
of bone fractures.
However, the
researchers stress, women treated with proper levels of the
hormone face no heightened risk of bone breaks.
Women taking replacement thyroid hormones
need to make sure their levels are being carefully monitored
and kept within the normal range.
The thyroid gland churns out hormones
that help regulate the body's metabolism. Normally, the gland
works like a thermometer, adjusting its output based on the
body's needs. But the gland can become either overactive or
underactive. An underactive thyroid is typically treated with
thyroid replacement hormone.
However, some evidence suggests excess
thyroid hormone (through either an overactive thyroid
or thyroid replacement treatment) could
decrease bone mass.
Waning bone mass puts a woman at risk
of developing the brittle-bone disease osteoporosis.
The investigators found that women with
elevated levels of thyroid hormone were three times more likely
than women with normal levels to fracture a hip, and four
times more likely to sustain a spine fracture.
The majority of the women with high levels
of thyroid hormone were receiving too much thyroid replacement
hormone. Some however, were producing too much of the hormone
in their own bodies.
Researchers suspect that elevated levels
of thyroid hormone may cause high bone turnover, leading to
weakened bones. ("Too much" thyroid replacement
hormone was defined as a TSH level of "less than 0.1"
) Bone is constantly being broken
down and rebuilt. That rate appears to be affected by excess
levels of thyroid hormone.
However, women
taking the proper amount of thyroid replacement were at no
higher fracture risk.
An important point is if your thyroid
level was in the normal range, there's been no clear evidence
that thyroid hormone was bad for you.
Annals of
Internal Medicine April 3, 2001;134:561-568
COMMENT:
By Mary Shomon (About.com
Thyroid Expert)
Last year, an article I did on the
subject, The
Thyroid Treatment/Osteoporosis Controversy, presented
a number of research studies that found no link between suppressive
doses of thyroid hormone and increased bone loss or fracture
risk, as well as other studies that, like the current one,
support this theory.
Not many physicians do maintain their
patients at suppressive doses such as the level described
in this study. Typically, only thyroid cancer survivors --
whose TSH is suppressed to prevent cancer recurrence -- are
kept at these levels.
Occasionally, a physician will treat
patients with suppressive doses to reduce symptoms, but this
is not common. If a physician is maintaining a patient at
a suppressive dose, they will typically prescribe supplemental
calcium, as well as an exercise program for building and maintaining
bone. For more details, read The
Thyroid Treatment/Osteoporosis Controversy.
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