Inverse Relationship of BMI to TSH and Risk of Papillary Thyroid Cancer in Surgical Patients.

BACKGROUND: Obesity and thyroid cancer has increased in recent decades. Thyroid malignancy is linked with elevated thyroid-stimulating hormone (TSH) levels, which may have a positive association with body mass index (BMI). This study examines obesity and TSH level effect on papillary thyroid cancer (PTC) risk in a surgical population. METHODS: A retrospective review of prospectively collected data for 991 patients who underwent thyroidectomy at a single institution was performed. Patients were stratified according to BMI into three groups: nonobese (18.5-29.9 kg/m2), obese (30-39.9 kg/m2), and morbidly obese (≥40 kg/m2). Further subdivisions into benign and malignant outcomes based on final pathology were compared with preoperative TSH levels. Subanalyses according to sex were also performed. RESULTS: Of 517 patients with PTC, rate of malignancy (ROM) decreased (55% versus 48% versus 41%, P < 0.05) as BMI increased with a concomitant decrease in average TSH levels (1.75 versus 1.69 versus 1.41 mU/L), respectively. According to sex, decreased ROM (53% versus 44% versus 42%, P < 0.05) and TSH (1.79 versus 1.70 versus 1.33 mU/L), respectively, with increased BMI was identified in women. However, decrease of ROM was not significant in men with increasing TSH levels as BMI increased. Male sex was associated with increased PTC risk (OR, 1.916; 95% CI, 1.331-2.759), whereas obesity with reduced PTC risk (OR, 0.736; 95% CI, 0.555-0.976). CONCLUSIONS: Higher BMI correlates with decreased PTC rates and lower TSH levels and suggests other factors may be involved in thyroid tumorigenesis. Obese patients with thyroid cancer should not be managed differently compared with nonobese patients.