A new study linked a widely used drug treatment for Type 2 diabetes to low levels of thyroid-stimulating hormone (TSH) that increases one's risk to hypothyroidism.
Hypothyroidism is a condition in which the thyroid glands fail to produce sufficient thyroid hormone resulting to slower metabolism. It is estimated that about 10 million Americans have the condition and some are not even aware. Common symptoms include fatigue, weight gain, dry hair and skin, cold intolerance, muscle cramps, memory loss and depression.
Researchers from the Department of Oncology at McGill University in Montreal studied data from 74, 300 patients who were treated with sulfonylurea, a drug also used to treat diabetes, and metformin.
Metformin is a common treatment for those diagnosed with Type 2 diabetes to help them manage their blood control levels. However, earlier studies found that the drug may have been causing reduced production of thyroid-stimulating hormones.
During the 25-year study period, 5,689 of the participants developed hypothyroidism while 59,937 had healthy thyroids. There were 495 cases of low-thyroid stimulating hormone per year on those with hypothyroidism as compared to 322 cases per year of those with normal thyroids.
Those with treated hypothyroidism were exposed to a 55 percent increased risk of insufficient TSH levels after receiving metformin monotherapy as compared to those who were given sulfonylurea. Sulfonylurea is another treatment for Type 2 diabetes that increases the amount of insulin produced by the pancreas.
"The results of this longitudinal study confirmed that the use of metformin was associated with an increased risk of low TSH levels in patients with treated hypothyroidism," said Dr. Laurent Azoulay from the Lady Davis Institute, Jewish General Hospital and the Department of Oncology at McGill University said in a press release.
Low levels of thyroid hormones can lead to further health complications such as cardiovascular diseases, fractures, and goiter.
The researchers noted that further study is needed to establish a direct cause-and-effect on metformin and lower TSH levels. Other health experts agreed on this.
"This study did not contain any measurements of the two forms of thyroid hormone in the blood. That data might help clarify why the TSH is suppressed," Dr. Gerald Bernstein, director of the diabetes management program at the Friedman Diabetes Institute at Mount Sinai Beth Israel in New York City told WebMD News.
Further details of the study were published in the Sept. 22 issue of the Canadian Medical Association Journal.
