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.