Effects of L-Thyroxine Therapy on Circulating Leptin and Adiponectin Levels in Subclinical Hypothyroidism: A Prospective Study

Abstract

Subclinical hypothyroidism (SCH) is defined by increased thyrotropin (TSH) and normal free thyroxine (fT4) levels. Controversial data are available regarding the effects of SCH on adipose tissue. Adiponectin and leptin are two major adipokines secreted from adipose tissue. We aimed to determine the levels of adiponectin and leptin in women with SCH and potential effects of L-thyroxine therapy on those levels. Forty three women with SCH and 53 age- and BMI-matched healthy euthyroid control women were included. Adiponectin and leptin levels, total cholesterol (TC), triglycerides (TG), HDL-, and LDL cholesterol, fat mass (FM) and fat-free mass (FFM) were determined in all participants. Patients received L-thyroxine treatment for 6 months after which all measurements were repeated. Patients with SCH and controls had similar baseline values for adiponectin, leptin, lipids, FM and FFM. All patients reached euthyroid status after 6 months of replacement therapy. Treatment resulted in an increase in adiponectin (p <0.01) and a decrease in leptin levels (p <0.05). Lipid levels, FM and FFM did not show a significant change. Achievement of euthyroid status by replacement therapy increases adiponectin and decreases leptin levels in women with SCH in this prospective study independent of a change in body fat mass.