Background

Obesity has become one of the most significant public health challenges. This can cause physiological disorders that increases the mortality and morbidity risk. Also contributes in the pathogenesis of several endocrine abnormalities, including thyroid dysfunction. The obesity has been associated with high levels of TSH. Some clinical assays had been demonstrated a positive correlation between obesity and levels of TSH. We performed an observational study, evaluating patients with morbid obesity submitted to bariatric surgery. We included 30 patients (15 patients with Gastric Bypass) and 15 patients with Gastric Sleeve at Centro Medico Nacional de Occidente in Guadalajara, Jalisco, Mexico. Clinical, anthropometric, biochemical, and hormonal parameters were evaluated, before the Bariatric Surgery and four weeks after Bariatric Surgery. Pre-surgical mean free tiroxine (T4) (ng/dL) was 1.2 +- 0.3, Pos-surgical mean free tiroxine (T4) (ng/dL) was 1.1 +- 0.2. Pre-surgical mean TSH (µUI/dL) was 2.99 +- 0.8, Pos-surgical mean TSH (µUI/dL) was 2.42 +- 0.6. TSH levels significantly decreased in the obese patients after surgery; 2.99 +- 0.8 vs. 2.42 +- 0.6 before and 4 weeks after surgery, respectively. Free thyroxine (T4) (ng/dL) levels significantly decreased in the obese patients after surgery; 1.2 +- 0.3 vs. 1.1 +- 0.2 before and 4 weeks after surgery, respectively. TSH decreased significantly over time. In euthyroid patients with morbid obesity, weight loss induced by bariatric surgery promotes a significant decline of the increased TSH levels. This decrement of TSH is progressive over time after surgery, but without significantly association with loss of weight or BMI.