More than a century ago, a 46-year-old woman's life was saved when her dangerously underactive thyroid was treated with dried sheep's thyroid. Since then, thyroid hormone therapy has become the gold standard of treatment for hypothyroidism (an underactive thyroid gland), though the hormone, called levothyroxine, no longer comes from the minced up glands of animals.
In fact, levothyroxine (produced in a lab) is among the top five prescription drugs sold in North America. Over nine million prescriptions for Synthroid, one brand of levothyroxine, were written in Canada in 2005, making it the second top-selling drug next to cholesterol-lowering Lipitor.
These drugs, also known as L-thyroxine or T4, provide for the thyroid hormone if your thyroid gland is unable to make enough. And there are lots of underactive thyroids out there, because hypothyroidism affects three percent of the world. M. Sara Rosenthal, a thyroid expert, writes in The Thyroid Sourcebook that roughly four to seven percent of people over the age of 60 are hypothyroid.
An aging society that's increasingly hypothyroid explains, in part, the zillions of pills taken annually; but many younger people also take it to address fatigue, cold intolerance, depression and a host of other everyday maladies. There's also the view that thyroid supplements work as a weight management tool. So no wonder that this medication has shifted in the public's mind from life-saving medicine to life-enhancing therapy.
Now, a recently published study underlines the fact that thyroid supplements are potent medicines that should be monitored annually by a doctor and respected by those who take it. In the study, conducted by a team of researchers from Toronto, elderly people who were taking medium to high doses of levothyroxine were found to have had two and a half to three times greater chance of suffering from a fracture than those who were taking a lower dose.
Eighty-eight percent of the people studied were women, says Dr. Lorraine Lipscombe, research scientist at the Women's College Hospital Research Institute. "We wanted to see if there was an effect of levothyroxine treatment on the risk of fracture on persons over the age of 70. Results of our study suggest that maybe these people were getting too much thyroid because their fracture risk was higher with these higher doses."
Of the 213,511 people studied, a total of 22,236 (10.4 percent) of people experienced at least one fracture during the study period which was between 2002 and 2007. The study was done using population health data bases in Ontario; hospital records were used to identify fractures.
The majority of people are diagnosed with hypothyroidism in middle age, she explains. "While initially they get monitored to try to get the right dose, once the right dose is determined, often times they stay on the same dose for years." As people age, their thyroxine requirements fall but their doses often remain unchanged into old age. "We are beginning to realize that the dose that was appropriate for them in middle age is no longer appropriate for them as they enter older age. People who are on thyroxine should go to the doctor and make sure that they have had a recent blood test to see if they're on the right dose."
Regular dose monitoring may not be done for a variety of reasons: People who have been on one dosage for years and who feel good on it may assume that the dosage is still appropriate; doctors themselves may overlook their patients' need for a blood test (which is necessary to confirm thyroid hormone levels), particularly when older patients present with other problems that need tending to.
Experts report that too much thyroxine speeds up the body's metabolism and thins the bones, but it isn't just the fractures that are worrisome. Too much of this hormone increases the risk for serious heart arrythmias, and muscle weakness. "Our job with this study was to raise awareness that thyroid hormone levels need monitoring. We estimate that about 20% of seniors are taking levothyroxine, so this has a big impact."
The study, published in the British Medical Journal, suggests that the ideal dose of thyroid drugs should take the age of the patient into consideration. In Canada, one levothyroxine brand is called Synthroid; another is Eltroxin. If you're taking either, do not stop them, but check with your doctor at your next appointment about whether your dose needs to be changed.
The butterfly gland
The thyroid, a butterfly shaped gland situated at the base of the throat, naturally secretes a hormone that is responsible for regulating the metabolism rate of the body. Hypothyroidism, the lack of thyroid hormone, is treated with levothyroxine.
The Thyroid Sourcebook
M. Sara Rosenthal's excellent book tells you everything you need to know about the thyroid, its diseases and disorders. The thyroid cancer survivor and consumer health specialist also covers the latest treatment options and complementary therapies, the best tests, and how to spot bogus websites in the thyroid e-health movement.