Before treatment patients with hyperthyroidism weighed less than the comparison group. After treatment men were 1.7 times and women were 1.3 times more likely to develop obesity. Weight gain occurred mostly in the first 6 months of treatment but continued until 24 months. A total of 65% of patients gained 5% of their weight and 38% gained 10% or more. Men gained on average 17.6 lbs and women gained about 12.1 lbs. Average weight gain was about 11.8 lbs for patients who were treated with medication, 12.3 lbs for those who had RAI treatment without developing hypothyroidism, and 15.6 lbs for those who had RAI treatment and developed hypothyroidism. Other risk factors for more weight gain were Graves’ disease as the cause of the hyperthyroidism, an elevated TSH after treatment, or the requirement of thyroid hormone replacement. The amount of weight gain was associated with the severity of hyperthyroidism at time of diagnosis and patients who had reported weight loss prior to treatment had more weight gain.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Treatment of hyperthyroidism with RAI or anti-thyroid medications is associated with an increased risk of gaining weight and even developing obesity. This risk is slightly higher with RAI therapy compared to medications. Patients who had surgery were not included in the study so we do not have a comparison.
The risk of weight gain can be very scary, however, hyperthyroidism needs to be treated otherwise it can become very severe and even lead to deadly complications. The most important step to control weight gain from any cause is to increase the awareness of providers and the patients. Strategies to prevent weight gain should be a part of the initial treatment plan for hyperthyroidism.
— Ebru Sulanc, MD, FACE