Decreased thyroid function, or hypothyroidism, is commonly associated with weight gain. But contrary to popular belief, effective treatment with levothyroxine (LT4) to restore normal thyroid hormone levels is not associated with clinically significant weight loss in most people. The study that led to this surprising finding will be presented by researchers from Boston University Medical Center at the 83rd Annual Meeting of the American Thyroid Association, October 16-20, 2013, in San Juan, Puerto Rico.
In "Weight Change after Treatment of Hypothyroidism," SY Lee, LE Braverman, and EN Pearce describe the retrospective review of patients with newly diagnosed primary hypothyroidism over an 8-year period, not caused by thyroid cancer or other forms of disease or associated with pregnancy or use of prescription weight loss medication.
About half (52%) of the patients lost weight up to 24 months after initiation of treatment with LT4. Overall, weight loss was modest, with a mean weight loss of 8.4 + 9.7 lbs.
"Because obesity and hypothyroidism are very common, there are many patients who have both conditions," says Ronald J. Koenig, M.D., Ph.D, Program Committee Co-Chair, and Professor, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor. "These patients (and sometimes their physicians) often assume the hypothyroidism is causing the obesity even though this may not be the case. This study is important because it shows, unfortunately, that only about half of hypothyroid patients lose weight after the successful treatment of their hypothyroidism. It will be interesting and important to have follow up data to know whether the patients that lose weight are the ones most in need of weight loss, and to know how significantly their weight loss contributed toward achieving a normal body weight."
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