Persistent Cellular Metabolic Changes after Hemithyroidectomy for Benign Euthyroid Goiter

Background: The significance of perturbations of thyroidstimulating hormone (TSH) and thyroid hormones within the laboratory reference ranges after hemithyroidectomy is unknown. Our aim was to examine changes in TSH and thyroid hormones after hemithyroidectomy for benign euthyroid goiter, focusing on tissue response by examining the mitochondrial membrane potential (MMP) of peripheral blood mononuclear cells (PBMCs) and basal oxygen consumption (VO2). Materials and Methods: In a prospective study on 28 patients and controls, we examined serum TSH and thyroid hormones before hemithyroidectomy and 1, 3, 6 and 12 months after hemithyroidectomy for benign euthyroid goiter. In the hemithyroidectomy group, flow cytometry was used to measure the MMP of tetramethylrhodamine methyl ester (TMRM)-and MitoTracker Green (MTG)stained PBMCs, and VO2 was measured by an Oxycon Pro apparatus. Results: One year after hemithyroidectomy, TSH had increased from a median of 0.97 mIU/l (interquartile range, IQR: 0.69-1.50 mIU/l) to 2.10 mIU/l (IQR: 1.90-3.00 mIU/l; p < 0.001); free thyroxine (fT 4) had decreased from a median of 16.0 pmol/l (IQR: 14.9-17.0 pmol/l) to 14.8 pmol/l (IQR: 14.1-16.4 pmol/l; p = 0.009), whereas total triiodothyronine variations did not differ from those in controls. Concomitantly, the MMP of TMRM-and MTG-stained PBMCs was increased by 58% (p < 0.001) and 22% (p = 0.008), respectively. VO2 was increased by 14% (p = 0.01). Conclusion: Hemithyroidectomy for benign euthyroid goiter induced persistently increased TSH and decreased fT(4), sustained mitochondrial hyperpolarization and increased VO2. Our results demonstrate a decrease after hemithyroidectomy of the metabolic state to which the individual is adapted, with persistent cellular metabolic changes in a hemithyroidectomized patient group which is normally considered clinically and biochemically euthyroid. (C) 2014 European Thyroid Association Published by S. Karger AG, Basel.