Circulating adiponectin concentrations were related to free thyroxine levels in thyroid cancer patients after thyroid hormone withdrawal.

Because it is unclear whether adipose-derived hormones are related to thyroid hormone metabolism, this study evaluated the relationship between adiponectin concentrations and changes in the thyroid hormones in athyreotic patients after thyroid hormone withdrawal. Twenty-eight athyreotic thyroid cancer patients (4 male and 24 female; mean age, 52.2 +/- 11.3 years) were analyzed on the final day of levothyroxine treatment and 1 day before serum thyroglobulin and radioiodine scanning examinations after an average of 4 weeks of thyroid hormone withdrawal. Evaluations included analysis of thyroid function test, serum adiponectin, body composition by bioimpedance analysis, and insulin sensitivity index as determined by the homeostasis model assessment of insulin resistance (HOMA-IR). Discontinuation of thyroid hormone treatment resulted in a significant change in thyroid-stimulating hormone (82.1 +/- 9.8 vs 1.0 +/- 0.4 mL/L, P < .05), free thyroxine (FT4) (5.7 +/- 0.4 vs 18.7 +/- 2.3 pmol/L, P < .05), and free triiodothyronine levels (1.8 +/- 0.2 vs 3.4 +/- 0.2 pmol/L, P < .05) as compared with the prewithdrawal values, whereas circulating adiponectin levels (5.7 +/- 0.6 vs 5.4 +/- 0.6 mg/L), body fat mass (20.3 +/- 1.2 vs 19.4 +/- 1.2 kg), and insulin sensitivity index (1.8 +/- 0.2 vs 2.2 +/- 0.3) remained unaltered. A positive correlation between adiponectin and FT4 (r = 0.61, P < .01) independent of age, sex, fat body mass, HOMA-IR, and other potential covariates known to affect thyroid hormone metabolism, such as renal and liver functions, was observed after thyroid hormone withdrawal. In addition, baseline circulating adiponectin levels were correlated with a diminished postwithdrawal reduction of FT4 concentrations after adjusting for baseline FT4 levels and changes in body mass index, fat body mass, and HOMA-IR (r = 0.71, P < .01). In conclusion, adiponectin concentrations were associated with FT4 levels in the athyreotic patients after thyroid hormone withdrawal. The relevant roles of adiponectin in the regulation of thyroid hormone metabolism require further investigation.