Artificially Induced Thyroid Suppression in Sickle Cell Disease

Depression of thyroid function in patients with hemoglobin SS disease might be expected to: (1) reduce tissue oxygen consumption, (2) decrease erythrocyte 2, 3-diphosphoglycerate, (3) decrease p50, (4) increase the average level of erythrocyte oxygenation, and (5) increase in vivo red cell survival with associated improvement in anemia and possibly in musculoskeletal symptoms. Accordingly, 150-200 mg of 6-n-propylthiouracil were administered three times a day for 143 days to a 21-yr-old male with hemoglobin SS disease. Thyrosuppression was indicated by typical symptoms and appropriate changes in physical and biochemical parameters. Detailed hematologic follow-up, including multiple measurements of red cell mass, ⁵¹Cr erythrocyte survival, red cell 2,3-diphosphoglycerate, and p50, showed no change. Furthermore, musculoskeletal symptoms continued in the pattern characteristic of the euthyroid state. A possible explanation for the lack of any change in clinical status may be that decreased cardiac output, with attendant prolonged circulation time and increased tissue oxygen demand per red cell per unit time, offset the absolute decrease in tissue oxygen consumption. The study provided an opportunity to make detailed clinical observations of sickle cell disease in association with thyroid suppression. The results suggest that thyrosuppression within the limits of symptomatic and physiologic tolerance has no therapeutic application in the clinical management of hemoglobin SS disease.