Erythrocyte zinc concentration as an indicator to distinguish painless thyroiditis-associated transient hypothyroidism from permanent hypothyroidism

Abstract

There are two clinical presentations of hypothyroidism, permanent hypothyroidism (PH) and transient hypothyroidism (TH). PH patients require a lifelong T4 supplementation. In contrast, TH spontaneously resolves within several months and therefore TH patients basically need no or short-term supplementation. abstract. Red blood cell (RBC) zinc (Zn) concentration reflects a patient's mean thyroid hormone level over the preceding several months. The aim of this study was to examine whether RBC Zn level can be used as an indicator to distinguish painless thyroiditis-associated transient hypothyroidism (TH) from permanent hypothyroidism (PH). RBC Zn level was measured in 30 untreated PH patients with Hashimoto's thyroiditis and 7 untreated TH patients with painless thyroiditis in whom preceding transient thyrotoxicosis had been confirmed. RBC Zn concentration was significantly lower in TH patients than that in PH patients. There was a positive correlation between RBC Zn and serum TSH, and the latter was clearly lower in TH patients than that in PH patients. However, RBC Zn level was again significantly lower in TH patients than PH patients despite of the comparable serum TSH levels in both groups when RBC Zn was evaluated in patients with serum TSH levels of less than 50 mU/L. Thus TH patients could be identified with RBC Zn measurement, allowing us avoidance of unnecessarily prolonged T4 administration to them.Key words: Hypothyroidism, Zinc, Red blood cell, Painless thyroiditis However, there are few indicators that can be used for this purpose.Thyroid hormone inhibits the synthesis of red blood cell (RBC) carbonic anhydrase I (CAI) [6] with which most of zinc (Zn) in RBC is associated [7], thus decreasing RBC Zn concentrations [8]. We have previously shown that patients with Graves' hyperthyroidism have a RBC Zn level clearly lower than that of patients with destructive thyroiditis [9,10]. Our data have therefore demonstrated that the RBC Zn concentration reflects a patient's mean thyroid hormone level over the preceding several months as glycosylated hemoglobin level does in diabetic patients [11]. In contrast, RBC Zn levels in hypothyroid patients have received less attention. In our previous studies [9], hypothyroid patients have a RBC Zn concentration similar to that of healthy controls. However, RBC Zn level was not measured individually in each form of hypothyroidism. Considering the thyroid hor-

Evaluation of inflammatory and oxidative biomarkers in children with well-controlled congenital hypothyroidism

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Efeito Dos Nutrientes E Substâncias Alimentares Na Função Tireoidiana E No Hipotireoidismo

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