Abstract:

Aim: Influences of thyroid hormones on leptin levels are controversial. We aimed to evaluate serum leptin levels in women with hyperthyroidism before and after treatment. Material and Methods: Newly diagnosed 27 hyperthyroid women (age 35±10 years, body mass index (BMI) 26.21±5.44 kg/m²) and 30 healthy women were included the study. BMI, body fat mass (FM) and fat percent (F%) were determined. Standard oral glucose tolerance test (OGTT) was performed and area under the curve (AUCglu120) of glucose for determined insulin resistance was measured in all subjects. Serum leptin levels were determined with radioimmunoassay before and after treatment. Results: Serum leptin levels in hyperthyroid patients were lower than control subjects (19.95±19.81 and 35.90±22.73 ng/dl, p<0.01). Leptin levels in hyperthyroid state were also lower than in euthyroid state (19.95±19.81 and 24.54±19.99 ng/dl, p=0.028) in the hyperthyroid group. With the treatment of hyperthyroidism serum leptin levels showed significant increase and it became indifferent from control subjects. However antropometric parameters did not show any significant difference with the treatment. AUCglu120 values in hyperthyroid women were higher than control subjects (165704±3276 and 12567±2102 mg.min/dl, respectively and p<0.001). After the treatment, AUCglu120 values decreased and it became indifferent from control subjects in hyperthyroid women. Conclusions: Serum leptin levels were low in women with hyperthyroidism and hypoleptinemia can be corrected with tretament of hyperthyroidism. Low serum leptin levels in hyperthyroidism can not be explained with differences in body fat and BMI. More importantly, glucose disposal may impair in hyperthyroidism and it may recover with euthyroidism independent from serum leptin levels. Key Words: Hyperthyroidism, leptin, insulin resistance, BMI

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