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Hyperthyroidism treatments may accelerate increases in weight
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Obesity was shown to be more likely to develop in a cohort of adults with hyperthyroidism who received treatment for the condition vs. a background population, with radioiodine therapy applications playing a large role in this trend, according to findings published in Thyroid.
“Hyperthyroidism, characterized by excess concentrations of circulating thyroid hormones, commonly presents with weight loss,” Kristien Boelaert, MD, PhD, of the University of Birmingham in the U.K., and colleagues wrote. “Weight regain may therefore be expected following normalization of thyroid function. However, it is not clear if this weight regain reflects the desirable replenishment of premorbid weight or an undesirable ‘overshoot’ potentially contributing to increased risks of obesity.”
Boelaert and colleagues conducted a longitudinal study using data from 1,373 adults with overt hyperthyroidism from the Thyroid Clinic Database at the University Hospitals Birmingham NHS Foundation Trust (mean age, 49 years; 77% women) and 10,984 participants in the Health Survey for England (mean age, 48 years; 77% women), which they categorized as the background population. A regimen of antithyroid medications and/or radioiodine therapy was undertaken by the participants with hyperthyroidism from 2000 to 2014. Participants were then followed for a maximum of 36 months, with the researchers calculating BMI based on weight and height measurements taken at baseline and during follow-up visits. The researchers also measured levels of thyroid-stimulating hormone, triiodothyronine and thyroxine at baseline and during follow-up.
Thirty-seven percent of men with hyperthyroidism developed obesity upon discharge, which compared with a proportion of 26% for those in the background population (P < .001), according to the researchers, who noted that the proportion of women with obesity was 26% in the background population and 32% for those treated for hyperthyroidism at study’s conclusion (P < .001). Men with treated hyperthyroidism had a median BMI of 28.4 kg/m2 and men in the background population had a median BMI of 27.1 kg/m2 upon discharge (P < .001). Women with treated hyperthyroidism had a median BMI of 27.2 kg/m2 and women in the background population had a median BMI of 26.1 kg/m2 when the study finished (P < .001).
Sixty-five percent of the participants with treated hyperthyroidism experienced at a least a 5% jump in weight and 38% gained at least 10% more weight during treatment, with the researchers noting that 6 kg was the mean weight gain for the entire population, with 8 kg added for men and 5.5 kg added for women on average (P < .001). When compared with the background population, men were 1.7 times more likely to develop obesity (OR = 1.7; 95% CI, 1.3-2.2) and women were 1.3 times more likely to reach the threshold for the condition (OR = 1.3; 95% CI, 1.2-1.5).
The researchers also found that there was an average 7.1 kg increase in weight for participants who were treated with radioiodine therapy and went on to have hypothyroidism. Meanwhile, respective increases of 5.4 kg and 5.2 kg were observed in those who were treated with antithyroid medications and those who were treated with radioiodine therapy but did not reach hypothyroidism. Participants who underwent radioiodine therapy gained 0.6 kg more than those who took antithyroid medications (P < .001), according to the researchers, who further noted that weight was 0.5 kg higher for those with elevated TSH vs. those without such measures (P < .001) and 0.3 kg higher for those with low T4 vs. those with normal levels (P < .001). An 0.4 kg increase in weight was also observed for those who underwent levothyroxine replacement vs. those who did not (P < .001).
“All interplaying factors may be affected during and following the treatment for hyperthyroidism, although the exact mechanisms and specific effects of different antithyroid treatments remain elusive,” the researchers wrote. “We postulate that discussion of the risk of excess weight gain should be undertaken and advocate weight management support approaches for patients with hyperthyroidism.” – by Phil Neuffer
Disclosures: The authors report no relevant financial disclosures.
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