Circulating leptin levels are not influenced by thyroid status in hypothyroid and euthyroid women.

OBJECTIVES: Leptin regulates body weight by suppressing food intake and increasing energy expenditure. Alterations in thyroid hormone levels are also associated with changes in body weight but the effect of thyroid hormone deficiency on serum leptin in humans is unclear.

DESIGN AND METHODS: The aim of this study was to measure leptin levels and to investigate their associations with thyroid hormones in 22 women with severe hypothyroidism after total thyroidectomy, and in a group of 22 healthy euthyroid control female subjects matched for age and body mass index (BMI). Their plasma leptin, free thyroxine, triiodothyronine and TSH were measured.

RESULTS: Leptin levels in subjects and controls were (pg/mL) 18761.64+/-16973.96 and 18729.19+/-18014.05, respectively, p=0.9; leptin did not correlate with free thyroxine, triiodothyroinine and TSH: r=0.1039 and p=0.6453, r=0.0113 and p=0.9602, and r=-0.0525 and p=0.8165 for leptin and FT4, leptin and FT3, and leptin and TSH, respectively in subjects; r=-0.00056 and p=0.9980, r=0.248727 and p=0.2643, and r=-0.046919 and p=0.8357 for leptin and FT4, leptin and FT3, and leptin and TSH, respectively in controls. Leptin levels did not differ between subjects and controls and they did not correlate with thyroid hormones.

CONCLUSIONS: Leptin levels are not influenced by hypothyroidism and do not correlate with thyroid hormones in euthyroid and hypothyroid women.