Subclinical hypothyroidism and its relation to obesity in patients before and after Roux-en-Y gastric bypass.

Background: Subclinical hypothyroidism (SH), defined as a raised serum thyroid-stimulating hormone (TSH) with a normal free thyroxine (FT4), is occasionally observed in morbidly obese patients.
Objectives: It is currently not known whether thyroid hormone treatment is indicated. The aim of the present study was to assess the changes in thyroid hormone levels in thyroxine-naïve patients with SH in response to weight loss induced by Roux-en-Y gastric bypass (RYGB).
Setting: General hospital specialized in bariatric surgery.
Methods: Serum levels of TSH and FT4 were measured at baseline in 503 patients presenting for RYGB. In patients diagnosed with SH, these measurements were repeated 12 months postoperatively.
Results: SH de novo was present in 71 out of 503 patients (14.1%). One-year follow-up was available in 61 out of 71 patients (86%). TSH level >10 mU/L was observed in 3 patients (.5%). RYGB induced a decrease in BMI from 47±8 kg/m(2) to 33±6 kg/m(2) at 12-month follow-up (P<.001), and this was associated with a decrease in TSH from 5.8±2.0 to 2.8±1.3 mU/L (P<.001) and a decrease in FT4 from 15.2±2.1 to 13.9±2.3 pmol/L (P<.001), respectively. SH completely resolved in 53 (87%) of the de novo cases.
Conclusion: The prevalence of SH de novo is high in morbidly obese patients. After RYGB it resolves in about 90% of patients. This high degree of spontaneous recovery suggests that follow-up alone is sufficient in the majority of patients.
(Copyright © 2015 American Society for Metabolic and Bariatric Surgery. Published by Elsevier Inc. All rights reserved.)