Objective: The aims of the study were to compare: a) the thermogenic responses in subclinical hypothyroidism (SH) and euthyroid state; b) the relationship between thermogenic response and leptin level.
Methods: Thirty women diagnosed with SH (mean age 39.9+/-4.1 yr; body mass index 23.2+/-2.5 kg/m(2)) were enrolled in the study. Thyroid function tests, leptin, and lipid profiles were measured during SH and after stable euthyroidism was recovered. Thermogenic response was measured by Water Immersion Calorimetry during SH and after the euthyroid state was attained.
Results: The mean level of thermogenic response was found to be 1.45+/-0.43 kcal/kg*h in women with SH. It changed to 1.54+/-0.77 kcal/kg*h (p=0.01) in the euthyroid state; the change was statistically significant. Mean level of leptin was found to be 7.22+/-2.6 ng/ml in SH; and 15.8+/-8.0 ng/ml in the euthyroid state. There was a positive correlation between leptin and free T(3) (r=0.460, p=0.009) levels in SH. There were positive correlations between leptin level and fat mass in SH (r=0.820, p=0.01) and in the euthyroid state (r=0.700, p=0.03).
Conclusions: No correlations were found between thermogenic response and leptin levels in SH and in the euthyroid state. Thermogenic response and leptin levels rose after the euthyroid state was recovered.