Weight changes in euthyroid patients undergoing thyroidectomy.

BACKGROUND: Thyroidectomized patients frequently report weight gain resistant to weight loss efforts, identifying their thyroidectomy as the event precipitating subsequent weight gain. We wished to determine whether recently thyroidectomized euthyroid patients gained more weight over 1 year than matched euthyroid patients with preexisting hypothyroidism.
METHODS: We performed a retrospective chart review of subjects receiving medical care at an academic medical center. One hundred twenty patients had their weight and thyroid status documented after thyroidectomy and achievement of euthyroidism on thyroid hormone replacement, and one year later. Three additional groups of 120 patients with preexisting hypothyroidism, no thyroid disease, and thyroid cancer were matched for age, gender, menopausal status, height, and weight. Anthropometric data were documented at two time points 1 year apart. We compared the weight changes and body mass index changes occurring over a 1-year period in the four groups.
RESULTS: Patients with recent postsurgical hypothyroidism gained 3.1 kg during the year, whereas matched patients with preexisting hypothyroidism gained 2.2 kg. The patients without thyroid disease and those with iatrogenic hyperthyroidism gained 1.3 and 1.2 kg, respectively. The weight gain in the thyroidectomized group was significantly greater than that in the matched hypothyroid group (p-value 0.004), the group without thyroid disease (p-value 0.001), and the patients with iatrogenic hyperthyroidism (p-value 0.001). Within the thyroidectomized group, the weight gain in menopausal women was greater than in either premenopausal women (4.4 vs. 2.3 kg, p-value 0.007) or men (4.4 vs. 2.5 kg, p-value 0.013).
CONCLUSION: Patients who had undergone thyroidectomy in the previous year did, in fact, gain more weight than their matched counterparts with preexisting hypothyroidism. In addition, all patients with hypothyroidism, even though treated to achieve euthyroidism, experienced more weight gain than both subjects without hypothyroidism and subjects with iatrogenic hyperthyroidism. The greatest weight gain in the thyroidectomized group was in menopausal women. These data raise the question of an unidentified factor related to taking thyroid hormone replacement that is associated with weight gain, with an additional intriguing effect of thyroidectomy itself. Menopausal status confers additional risk. These groups should be targeted for diligent weight loss efforts.