Red-blood-cell composition in thyroid disease.

Eight red-blood-cell (R.B.C.) consitituents were measured in ten patients with hyperthyroidism and in ten healthy subjects. Only R.B.C. sodium ([Na]) and zinc ([Zn]) differed much between the groups. Therefore, only these variables were measured in a larger group of untreated hyperthyroid patients. The increase in. R.B.C. [Na] and decrease in R.B.C. [Zn] were confirmed. The R.B.C. [Na] and [Zn] were related to each other and to the plasma-thyroid-hormone concentration. However, more patients had low R.B.C. [Zn] (91%) than had raised R.B.C. [Na] (50%). Further studies suggest that the R.B.C. [Zn] lags behind the clinical response when these patients are treated. These results suggest that the measurement of R.B.C. [Zn] may have a role in the diagnosis of hyperthyroidism.