Abstract
Several erythrocytic enzymes have been studied in children with hypothyroidism during the initial time of therapy with a combination of thyroxine and triiodothyronine: glucose 6-phosphate dehydrogenase, 6-phosphoglycerate dehydrogenase, lactic dehydrogenase, hexokinase, yruvate kinase, phosphoglycerate kinase, glutathione reductase and glutathione peroxydase. The mean activities of all enzymes were lower in untreated hypothyroid patients than the mean activities of a control group. During hormonal treatment, the enzyme activities increased nearly in all patients regardless of whether they were subnormal or in the normal range. This increase is due to an elevation of the erythropoiesis and represents a decrease of the mean age of the circulating red cells.