Abstract
Endocrine abnormalities are common in obesity, including altered thyroid function. The altered thyroid function of obesity may be due to a mild acquired resistance to the thyroid hormone. The aim of this study was to investigate the effect of weight loss after bariatric surgery (BS) on resistance to thyroid hormones in patients with extreme obesity compared with a control group. We performed an observational study evaluating patients with extreme obesity who underwent BS. We included 106 patients (83 women) and 38 controls (24 women). The primary endpoint was the thyrotroph thyroxine resistance index (TT4RI) and thyroid stimulating hormone (TSH) index (TSHRI). The parameters were studied before and after surgery. TSHRI and TT4RI were higher in the obese patients than in the control group. TT4RI and TSHI decreased significantly over time after surgery, with this decrease being associated with the excessive body mass index (BMI) loss and C-reactive protein (CRP). In extreme obesity, BS promotes a significant decrease in the increased TT4RI and TSHI. This decrease of TT4RI and TSHI is progressive over time after BS and significantly associated with excess BMI lost and CRP. Extreme obesity is characterized by a mild reversible central resistance to thyroid hormones.
Highlights
The main result of this study is that we have found that the indices of central resistance to TH are increased in patients with extreme obesity, and that weight loss after bariatric surgery (BS) leads to a decrease in these indices through direct or indirect mechanisms
We found increased indices of central resistance to TH in obese subjects which decreased after weight loss in accordance with the hypothesis that the increase of thyroid stimulating hormone (TSH) and free T4 (FT4) may represent a compensatory activation of the thyroid axis [12]
This study shows that in patients with extreme obesity, weight loss induced with BS through direct or indirect mechanisms brings about a decline in the increased indices of central resistance to thyroid hormones
Summary
Since 1980, the prevalence of obesity has continuously increased in most countries. The prevalence of obesity in the United States in 2013–2014 was 35% among men and 40.4% among women. The corresponding values for morbid obesity were 5.5% for men and 9.9% for women [2]. Recent analysis indicates that the prevalence in the United States of adult obesity and severe obesity will continue to increase [3]. A moderate 5% weight loss improves metabolic function in multiple organs simultaneously, and progressive weight loss causes dose-dependent alterations in key adipose tissue biological pathways [6]. Bariatric surgery (BS) using gastric bypass, or sleeve gastrectomy, compared with non-surgical obesity management, was associated with a more marked improvement in comorbidities and lower all-cause mortality [7]
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