Acute exogenous TSH administration stimulates leptin secretion in vivo

TSH-receptor (TSHR) has been found in a variety of cell types, including preadipocytes and adipocytes. In vitro, TSH-mediated preadipocyte and adipocyte responses include proliferation, differentiation, survival, and lipolysis. Objective: To measure the response of serum leptin to exogenous administration of recombinant human TSH (rhTSH) in vivo. Patients: One hundred patients with differentiated thyroid cancer already treated by total thyroidectomy and 131I remnant ablation were enrolled. Mean (GS.E.M.) body mass index (BMI) was 26.9G±0.6 kg/m2. Methods: Patients received a standard dose of rhTSH for measurement of thyroglobulin in the follow-up of their disease. Blood samples were taken for the assay of TSH and leptin before the first administration of rhTSH (time 0), and 24 h (time 1), 48 h (time 2), 72 h (time 3), and 96 h (time 4) after the first administration of rhTSH. Results: Significant mean serum leptin increments, with respect to basal value, were 16, 13, 18, and 11% at times 1, 2, 3, and 4 respectively. Significant positive correlations of leptin-area under the curve with respect to basal leptin levels (r=0.43; P <0.0001) and BMI (r=0.32; P <0.005) were observed. Conclusions: Acute rhTSH administration in hypothyroid subjects under L-thyroxine therapy produces a rise in serum leptin. This increase is proportional to the adipose mass suggesting that a functioning TSHR is expressed on the surface of adipocytes. The role that TSHR activation in adipocytes might play in physiological and pathological conditions remains a matter of investigation. © 2010 European Society of Endocrinology.