Thyroid Function Alteration in Obesity and the Effect of Bariatric Surgery

The most common endocrine disease in obesity is hypothyroidism and secondary endocrine alterations, including abnormal thyroid function, are frequent in obesity. It is unclear whether impaired thyroid function is the cause or the consequence of increased adiposity; furthermore, there are no clear data regarding the best way to dose levothyroxine for patients with both hypothyroidism and obesity, and the effect of bariatric surgery (BS). The aim of the present article is to review some controversial aspects of the relation between obesity and the thyroid: (1) Thyroid function in obesity and the effect of BS (2) Thyroid hormone treatment (THT) in obese patients with hypothyroidism and the effect of BS. In summary: In morbidly obese patients, TSH is moderately increased. Morbid obesity has a mild central resistance to the thyroid hormone, reversible with weight loss. In morbidly obese hypothyroid patients, following weight loss, the levothyroxine dose/kg of ideal weight did not change, albeit there was an increment in the levothyroxine dose/kg of actual weight. From a clinical practice perspective, in morbid obesity, diagnosing mild hypothyroidism is difficult, BS improves the altered thyroid function and THT can be adapted better if it is based on ideal weight.

Automated summary

The relationship between obesity and thyroid function has some controversial aspects, including the effect of obesity on thyroid function and the impact of weight loss surgery. In morbidly obese patients, there is a mild increase in TSH and a mild central resistance to thyroid hormone, which can be reversed with weight loss. After weight loss, the levothyroxine dose/kg of ideal weight remains unchanged but increases when calculated based on actual weight. Diagnosing mild hypothyroidism is difficult in morbid obesity, and bariatric surgery can improve abnormal thyroid function, with better adaptation of thyroid hormone treatment based on ideal weight.