Red blood cell carbonic anhydrase and zinc concentrations reflect a patient's mean thyroid hormone level over the previous two months.

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We have previously reported that T3, at a physiological free concentration, decreases the carbonic anhydrase I(CAL) concentration in both human erythroleukemic YN-1 cells, and burst-forming unit-erythroid (BFU-E)-derived cells. In the present study, the effect of T3 on CAI mRNA levels in various human erythroleukemic cell lines and BFU-E-derived cells was studied. Northern analysis of RNA extracted from erythroid cells revealed a CAT mRNA of 1.5 kilobases. T3 significantly decreased the levels of CAT mRNA in YN-1 and BFU-E-derived cells in a dose dependent manner. Incubation of T3-stimulated cells with actinomycin D prevented the decrease in CAL mRNA levels. By contrast, T3 had no effect on either concentrations of CAL or the levels of CAI mRNA in HEL and KU-812 cells. These results suggest that YN-1 and BFU-E-derived cells may be useful models for investigating T3 actions on CAI mRNA in human cells.Since most of the zinc (Zn) in human red blood cell (RBC) is present as the metal cofac … More tor of CAI, the concentration of RBC Zn as well as CAL decrease in patients with hyperthyroidism, and reflect the mean thyroid hormone concentration over the preceding months. In the present study, the concentration of RBC Zn was measured by a simple and easy method with a Zn-test Wako kit. A good correlation (r=0.97) was obtained between this method and atomic absorption spectrophotometry. The mean concentration of RBC Zn in 39 euthyroid controls was 12.6 + 1.3 mg/l, ranging from 10.4 to 15.1 mg/l. The RBC Zn concentrations in 38 patients with Graves' disease, in 10 with silent thyroiditis, in 3 with gestational thyrotoxicosis, in 19 with primary hypothyroidism and in 12 with hypothyroid phase of silent thyroiditis were 7.3*1.6 (3.2-9.8), 12.0*1.6 (9.5-14.2), 11.8*1.7 (10.5-13.7), 14.1*1.1(11.8-15.8), and 10.4*1.8 (8.7-13.2) mg/l, respectively. The concentration of RBC Zn was able to differentiate hyperthyroid Graves' disease from transient thyrotoxicosis except in 1 case and a better index than TSH-binding inhibitor immunoglobulin. Furthermore, it was able to differentiate primary hypothyroidism from hypothyroid phase of silent thyroiditis except 2 cases. These results indicate that measuring RBC Zn with the Zn-test Wako kit is very useful in the diagnosis of thyroid diseases. Less