Hypothyroidism is the most prevalent endocrine condition in obesity, and subsequent endocrine abnormalities, such as impaired thyroid function, are widespread. It is uncertain if decreased thyroid function is a cause or a result of obesity; also, there is no clear evidence on the optimum approach to dose levothyroxine for people with both hypothyroidism and obesity, as well as the effect of bariatric surgery (BS). The purpose of this article is to discuss some contentious elements of the relationship between obesity and the thyroid: (1) Obesity and thyroid function, as well as the influence of BS (2) The effect of BS on thyroid hormone therapy (THT) in obese patients with hypothyroidism. To summarise: TSH is moderately elevated in morbidly obese people. Morbid obesity is associated with a modest central resistance to thyroid hormone, which is reversible with weight loss. Following weight decrease in morbidly obese hypothyroid individuals, the levothyroxine dose/ kg of ideal weight did not alter, despite an increase in the levothyroxine dose/ kg of actual weight. In clinical practise, detecting mild hypothyroidism in morbid obesity is challenging; nevertheless, BS improves the altered thyroid function, and THT can be better adapted if it is based on optimal weight.
