Dissociation of leptin and body weight in hyperthyroid patients after radioiodine treatment

Abstract

OBJECTIVE: Leptin regulates energy production rates and body weight, which are frequently altered in hyperthyroidism. Data on a possible interaction between leptin and thyroid hormones are controversial. We assessed leptin serum concentrations, BMI, proportional fat tissue mass and thyroid hormones in hyperthyroid patients in a long-term follow-up after radioiodine therapy. DESIGN: The study included 28 hyperthyroid patients (mean age 66 y) before and up to one y after radioiodine therapy. Leptin and thyroid hormones, general parameters, BMI, proportional fat tissue (PFT) measurements by DEXA and thyroid morphology were recorded. Twenty-four age-matched euthyroid individuals (mean age 63 y) served as controls. RESULTS: At baseline, leptin concentrations were signi®cantly decreased in all hyperthyroid patients as compared to controls. One year after radioiodine therapy, 71% of the patients were euthyroid (group A) and 29% remained hyperthyroid (group B). BMI and PFT increased in both groups. While leptin concentrations remained low in group B, they normalised in group A after 6 to 12 months. Changes in leptin and thyroid hormone concentrations were positively correlated in group A patients (r 0.49, P 0.03) but not in patients remaining hyperthyroid. CONCLUSION: Our data indicate a dissociation in the regulation of plasma leptin and BMI as well as proportional fat tissue in hyperthyroid patients which may be attributable to differences in lean and adipose mass weight gain after radioiodine therapy or direct in¯uences of thyroid hormones on leptin regulation.

Circulating leptin and thyroid dysfunction

“…Two studies used measurement of body composition by DEXA scans, which allows better correlations to fat measures (51,88), and found that although serum leptin levels increased during the 12-month ATD treatment of thyrotoxic patients compared with baseline and in accordance with what was found in rats (57,58,62), there was no relationship between changes in serum leptin and total fat mass.…”

“…In contrast, when two large cross-sectional groups of female patients with either pre-treatment hyperthyroidism or hyperthyroidism during treatment were compared a difference was indeed found, with low serum leptin at the time of newly diagnosed hyperthyroidism and normal serum leptin in euthyroid patients treated with ATD. Thus, an effect of ATD to increase serum leptin could be suggested, which was later confirmed in a prospective study of ATD in Graves' disease (51) and in another study of patients with nodular toxic goiter before and up to one year after radioiodine therapy (88). In both these studies (51, 88) serum leptin changes were dissociated from body weight changes as measured by BMI and from proportional or actual fat mass as measured by DEXA, indicating different rates of lean and adipose mass weight gains during normalization of thyroid function, irrespective of whether this was achieved by radioiodine therapy (88) or ATD (51).…”

“…Based on the studies summarized in the previous section there is not enough evidence for a relationship between autoimmune thyroid disease and leptin. None of the studies found any correlation between serum leptin and thyroid autoantibodies, and four of the studies found evidence that thyroid function is more important than autoimmunity in determining serum leptin concentrations (78,81,84,88).…”

“…This was accounted for mainly by a decrease in BMI in overt hyperthyroidism. In other studies, BMI-matched healthy persons were used as controls (51,70,87,88), and in these studies mean serum leptin concentrations in the cross-sectional comparison were unchanged in hyperthyroid patients compared with controls, irrespective of whether hyperthyroidism was due to autoimmune Graves' disease (51,77,87) or toxic adenoma/multinodular goitre (87). In the study by Seven (87), only the patients with Graves' disease were hyperthyroid while the patients with multinodular goitre were studied after one month of ATD.…”

Obesity and Weight Loss: The Influence of Thyroid Hormone on Adipokines

“…There is few data available regarding the thyroid hormones and PAI-1. Studies have been focused on serum measurements, in severe hypothyroidism was found decreased PAI-1 levels [215], while in hyperthyroidism some studies show increased [113, 216,217], other decreased [83,218] as well as unaffected PAI-1 levels [219,220].…”