Background: Patients who undergo thyroidectomy often complain of weight gain, which they frequently attribute to inadequate thyroid hormone replacement. To assess the weight changes associated with thyroid hormone replacement or suppressive therapy after thyroidectomy, we measured the weights of patients before and after thyroidectomy and compared them to the weights of euthyroid patients with thyroid nodules who were being followed for many years.
Methods: The weights and heights of 67 women and 35 men who underwent total thyroidectomy for thyroid cancer were recorded before and for a mean of 8.3 years after thyroidectomy. All patients received either suppressive or replacement doses of levothyroxine. As a comparison group, 70 women and 22 men with goiter or thyroid nodules and were euthyroid had serial measurements of height and weight. They were followed for a mean of 7.6 years. The body mass index (BMI) and age-adjusted BMI percentiles were calculated. The weight, BMI, and BMI percentile changes were compared both unadjusted and adjusted for age, gender, thyrotropin (TSH) level, and duration between measurements.
Results: At baseline, patients with thyroid nodules were older (mean 50.4 years) than those with thyroid cancer (mean 45.8 years). There were no significant differences in baseline weight, BMI, or BMI percentile. The baseline TSH levels were lower for patients with thyroid cancer (mean 0.8 mIU/L) than for those with nodules (mean 1.8 mIU/L) (p=0.002). There were no significant differences between the changes in weight, BMI, or BMI percentile from the start to the completion of the study whether unadjusted or after adjustment for age, gender, TSH, and duration of follow-up.
Conclusions: Despite the perception of many patients that their thyroidectomy and thyroid hormone replacement or suppressive therapy is responsible for their subsequent weight gain, there were no significant differences in weight gain over time in comparison to a control group of euthyroid patients with thyroid nodules or goiter.