Thyroid Drugs May Raise Fracture Risk in Elderly
Many seniors may be at increased risk for fractures because they take «excessive» doses of drugs used to treat thyroid problems, a new study says.
The findings suggest that treatment targets may have to be modified in elderly patients with thyroid problems and that regular dose monitoring of thyroid drugs is essential into older age, the researchers said.
Reporting in the online April 28 edition of the BMJ, they examined the link between fractures and levothyroxine, a synthetic form of thyroid hormone, which is widely used to treat an underactive thyroid gland (hypothyroidism).
Many patients with hypothyroidism are diagnosed in early or middle adulthood. Even though their treatment requirements change as they age, many patients remain on the same drug dose. This can lead to excess levels of thyroid hormone, which increases the risk of fractures, especially in older women, the study authors explained.
They analyzed data from over 213,500 patients, aged 70 or older, in the province of Ontario, Canada, who filled at least one prescription for levothyroxine between April 1, 2002 and March 31, 2007. During the study period, more than 22,000 (10.4 percent) of the patients suffered at least one fracture.
Current and recent past users (who had discontinued the drug 15 to 180 days before the start of the study) had a significantly higher fracture risk than «remote» users (who had discontinued use of the drug more than 180 days before the start of the study).
Among current users, those who took high or medium doses of the drug were much more likely to suffer a fracture than those who took a low dose.
«Our findings provide evidence that levothyroxine treatment may increase the risk of fragility fractures in older people even at conventional dosages, suggesting that closer monitoring and modification of treatment targets may be warranted in this vulnerable population,» concluded Lorraine Lipscombe, a scientist at the Women’s College Research Institute in Toronto, and colleagues.
One expert wasn’t surprised by the findings.
«It has long been known that high or excessive doses of levothyroxine usage predispose [people] to increases in osteoporosis and the risk of fracture,» said Dr. Irwin Klein, director of the thyroid unit and associate chairman of the department of medicine at the North Shore-LIJ Health System in Manhasset, N.Y. «This study further confirms this finding in an elderly population of women who are inherently at risk for this occurrence.»
Klein also noted that the study underscores the need for preventive action.
«As the authors conclude, it is important to monitor thyroid blood tests — especially TSH levels — to prevent this potential adverse health burden,» he said.
Thyroid Disorders Overview
The thyroid is a small butterfly-shaped gland inside the neck, located in front of the trachea (windpipe) and below the larynx (voicebox). It produces two thyroid hormones – tri-iodothyronine (T3) and thyroxine (T4) – that travel though the blood to all tissues of the body.
Thyroid hormones regulate how the body breaks down food and either uses that energy immediately or stores it for the future. In other words, our thyroid hormones regulate our body’s metabolism.
Another gland, called the pituitary gland, actually controls how well the thyroid works. The pituitary gland is located at the base of the brain and produces thyroid-stimulating hormone (TSH). The bloodstream carries TSH to the thyroid gland, where it tells the thyroid to produce more thyroid hormones, as needed.
Thyroid hormones influence virtually every organ system in the body. They tell organs how fast or slow they should work. Thyroid hormones also regulate the consumption of oxygen and the production of heat.
Endocrinologists – physicians and scientists who study and care for patients with endocrine gland and hormone problems – study and treat several major disorders of the thyroid gland. We will briefly describe these disorders here. You can link to any of the thyroid conditions that you may wish to learn more about.
Too much thyroid hormone from an overactive thyroid gland is called hyperthyroidism, because it speeds up the body’s metabolism. This hormone imbalance occurs in about 1 percent of all women, who get hyperthyroidism more often than men. One of the most common forms of hyperthyroidism is known as Graves’ disease. This autoimmune disorder tends to run in families, although the exact nature of the genetic abnormality is unknown.
Because the thyroid gland is producing too much hormone in hyperthyroidism, the body develops an increased metabolic state, with many body systems developing abnormal function.
Too little thyroid hormone from an underactive thyroid gland is called hypothyroidism. In hypothyroidism, the body’s metabolism is slowed. Several causes for this condition exist, most of which affect the thyroid gland directly, impairing its ability to make enough hormone. More rarely, there may be a pituitary gland tumor, which blocks the pituitary from producing TSH. As a consequence, the thyroid fails to produce a sufficient supply of hormones needed for good health.
Whether the problem is caused by the thyroid conditions or y the pituitary gland, the result is that the thyroid is underproducing hormones, causing many physical and mental processes to become sluggish. The body consumes less oxygen and produces less body heat.
A thyroid nodule is a small swelling or lump in the thyroid gland. Thyroid nodules are common. These nodules represent either a growth of thyroid tissue or a fluid-filled cyst, which forms a lump in the thyroid gland. Almost half of the population will have tiny thyroid nodules at some point in their lives but, typically, these are not noticeable until they become large and affect normal thyroid size. About 5 percent of people develop significant sized nodules, greater than a half inch across (about 1 centimeter).
Although most nodules are not cancerous, people who have them should seek medical attention to rule out cancer. Also, some thyroid nodules may produce too much thyroid hormone or become too large, interfering with an individual’s breathing or swallowing or causing neck discomfort.
Other thyroid problems include cancer, thyroiditis (swelling of the thyroid gland), or a goiter, which is an enlargement of the thyroid gland.