Study Shows Connection Between Thyroidectomy and Weight Gain

Thyroidectomy illustrationMany patients who have had a thyroidectomy complain of weight gain despite efforts to lose weight. These patients believe their thyroidectomy was the factor that led to their weight gain.

Researchers from Georgetown University Medical Center in Washington, DC, examined whether patients who recently had a thyroidectomy and who were now euthyroid gained more weight in a 1-year period than matched euthyroid patients who had pre-existing hypothyroidism.

The study appeared online in November 2011 in the article “Weight changes in euthyroid patients undergoing thyroidectomy.” It will be published in the journal Thyroid.

Investigators performed a retrospective chart review of study participants who received medical care at an academic medical center.

In this study, 120 patients had their weight and thyroid status recorded after thyroidectomy and after achieving euthyroidism on thyroid hormone replacement—and then again 1 year later.

There were 3 additional groups, each consisting of 120 patients. The groups were divided by pre-existing hypothyroidism, no thyroid disease, and thyroid cancer, and the groups were matched for:

  • age
  • gender
  • height
  • menopausal status
  • weight

For each study participant, anthropometric data were documented 2 times, 1 year apart. The research team compared weight changes and body mass index changes that occurred over a 1-year period in the 4 groups.

Participants who had recent post-surgical hypothyroidism gained 3.1 kg during the year; matched patients with pre-existing hypothyroidism gained 2.2 kg during the year. Patients who did not have thyroid disease gained 1.3 kg, and those who had iatrogenic hyperthyroidism gained 1.2 kg.

Weight gain in the patients who had a thyroidectomy—even though they were treated to attain euthyroidism—was significantly greater than weight gain seen in the:

  • matched hypothyroid group (p=0.004)
  • group without thyroid disease (p=0.001)
  • patients with iatrogenic hyperthyroidism (p=0.001)

For patients who had a thyroidectomy, the greatest weight gain was seen in menopausal women. Weight gain in these women was greater than in premenopausal women (4.4 kg vs. 2.3 kg; p=0.007) or men (4.4 kg vs. 2.5 kg, p=0.013).

Theses findings raise the question of a factor that has yet to be identified but that is related to treating patients with thyroid hormone replacement linked to weight gain (with an additional intriguing effect of thyroidectomy itself). Menopausal status carries an additional risk. According to researchers, these patients should be targeted for diligent weight loss efforts.

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