Carbonic Anhydrase and Fetal Hemoglobin in Thyrotoxicosis

An adult patient with thyrotoxicosis had erythrocyte carbonic anhydrase deficiency and an abnormally high level of fetal hemoglobin. After treatment of the hyperthyroidism, the erythrocyte carbonic anhydrase level became normal and the level of Hb F dropped. Twelve other patients with hyperthyroidism and not related to this index case were studied. Most of them were already under treatment. Nine had erythrocyte carbonic anhydrase deficiency; two had an increase of fetal hemoglobin. The possible relationship of increase of fetal hemoglobin, erythrocyte carbonic anhydrase deficiency and thyrotoxicosis is discussed.