Thyroid Hormone and Weight Loss

One of the main functions of thyroid hormones is to regulate metabolism. With increased metabolism, weight loss can be achieved. Evidence suggests that thyroid hormones may actually improve body composition and reduce body weight while improving overall health:
1. Thyroid hormones helps reduce body weight mainly through regulating energy expenditure. [63-64]
2. Obese women appears to have low circulating levels of T4, suggesting that thyroid hormone deficiency is associated with weight gain. [65]
3. In people undergoing weight loss diets, higher levels of T3 and T4 are associated with significant reduction in body mass index (BMI). [66]
4. In overtly hypothyroid patients, T4 replacement therapy reduces weight by improving lean body mass. [67-68]
5. In obese patients, administration of fresh thyroid juice reduces body weight by promoting diuresis (increased urine production). [69]
6. In patients with hypothyroidism, T3 therapy is associated with a significant weight loss of 2.1 kg. [70]
7. In overweight patients, T3 and T4 combination therapy significantly decreases body weight. [71-72]
8. Thyroid hormones promote weight loss by regulating resting metabolic rate (the rate at which the body burns energy at rest). [73-74]
9. Combination therapy of T3 and T4 appears to be more effective in reducing body weight in obese patients compared to monotherapy. [75-84]
10. In rats, T3 promotes weight loss through regulation of lipid metabolism in the brain. [85]