Endocrine Abstracts

Background: TSH seems to be positively related to the degree of obesity and weight loss seems to induce a reduction in the TSH levels and T3Total. TSH is the first regulatory mechanism of total energy expenditure and T3 regulates energy metabolism and thermogenesis (1)

Objective: The aim of this study was to investigate the association between thyroid function and body mass index (BMI) in obese population. And evaluate the influence of weight reduction after gastric by-pass on thyroid hormone levels.

Design: Retrospective observational study

Setting: A single center study in Curitiba, Brazil.

Methods: We studied 215 obese patients (BMI 35–58.5 kg/m²), age between 18–65 years, baseline, 3, 6, 12, 24 months after laparoscopic Roux-en-Y gastric bypass (RYGBP). Participants with thyroid disorders were excluded.

Results: Baseline TSH concentration was not associated with baseline BMI (Pearson=0.003; P=0.971). There were a significantly decrease in serum TSH after RYGBP until 24 months (P=<0.001) (Figure 1), but did not correlate with weight loss (Pearson=0.08; P=0.303). Subclinical hypothyroidism prevalence was 9.3% (n=20) before RYGBP. At 12 months, 8.7% (n=17) of this patients had TSH<4.5 (P=0.003).

Limitations: This study is a retrospective review and did not employ controls, blinding, or randomization. Additionally, the thyroid antibodies did not evaluate.

Conclusion: Weight loss after the gastric bypass improved and normalized thyroid hormone levels. More studies are required to clarify the reason of decrease in serum TSH.

Figure 1