Background: Several endocrine abnormalities, including hypothyroidism and Cushing's syndrome (CS), are considered as causative factors of obesity. The aim of this study was to evaluate the prevalence of endocrine disorders and obesity-associated co-morbidities, as well as the impact of substantial weight loss.
Methods: Screening was performed in 433 consecutive morbidly obese patients (age 41 ± 12 years; BMI 47 ± 6.9 kg/m(2); women 76%). A 1-mg dexamethasone suppression test (1-mg DST) was conducted to exclude CS, and thyrotropin (TSH) was measured to exclude hypothyroidism. Insulin sensitivity was estimated from oral glucose tolerance tests employing the Clamp-like index. Examinations were carried out at baseline, as well as at 6 and 12 months postoperatively.
Results: The prevalence of CS was below 0.6%. Before surgery, TSH was elevated compared to an age- and sex-matched normal weight control group (2.4 ± 1.2 vs. 1.5 ± 0.7 μU/ml; p < 0.001). The NCEP criteria of metabolic syndrome (MetS) were fulfilled by 39.5% of the patients. Impaired glucose tolerance and diabetes mellitus were observed in 23.5% and 22.6%, respectively. Seventy-two percent were insulin resistant. During follow-up, weight (BMI 47 ± 6.9 vs. 36 ± 6.4 vs. 32 ± 6.6 kg/m(2); p < 0.001) and TSH decreased significantly (2.4 ± 1.2 vs. 1.8 ± 1.0 vs. 1.8 ± 1.0 μU/ml; p < 0.001). Serum cortisol was higher in the MetS(+)-group compared to the MetS(-)-group (15.0 ± 6.3 vs. 13.5 ± 6.3 μg/dl; p = 0.003).
Conclusions: CS appears to be a rare cause of morbid obesity. Normalization of slightly elevated thyrotropin after weight loss suggests that obesity causes TSH elevation rather than the reverse.