SERUM LEPTIN CONCENTRATIONS IN PATIENTS WITH THYROID-DISORDERS

OBJECTIVE Leptin, the obese gene product, is secreted exclusively by a dipocytes and is thought to act as a lipostatic signal that regulates body weight homeostasis. We previously reported that thyroid hormone i s one of the up-regulating factors of leptin in vitro, T3, at physiolo gical concentrations, stimulates leptin mRNA expression and leptin sec retion by 3T3-L1 adipocytes, The aim of this study was to explore the role of thyroid hormone in the regulation of leptin in humans, DESIGN AND PATIENTS A total of 59 non-obese women aged 38.4 +/- 1.8 years (me an +/- SEM) were studied: 19 patients with hyperthyroidism, 17 patient s with hypothyroidism, and 23 normal control subjects, The correlation between serum leptin concentrations and body mass index (BMI) was ana lyzed, and serum leptin levels were compared among the three groups, M EASUREMENTS Serum leptin concentrations were measured by radioimmunoas say, RESULTS Serum leptin concentrations after logarithmic transformat ion were correlated significantly (P < 0.05) with BMI in the hyperthyr oid (r = 0.46), the hypothyroid (r = 0.84), and normal (r = 0.63) grou ps, Even though age, body weight, and BMI were similar in all groups, serum leptin levels in the hypothyroid patients (5.30 +/- 1.12 mu g/l) were significantly (P < 0.05) lower than in the hyperthyroid and norm al groups (6.87 +/- 0.66 and 6.58 +/- 0.68 mu g/l, respectively). CONC LUSIONS These results indicate that thyroid hormone may play an import ant role in the appropriate secretion of leptin in humans.