Red cell 2,3-diphosphoglycerate and oxygen affinity of hemoglobin in patients with thyroid disorders.

We measured red blood cell 2,3-diphosphoglycerate (2,3-DPG), adenosine triphosphate (ATP), and the P50 value in vitro of the oxyhemoglobin dissociation curve, which is the oxygen tension at half saturation of hemoglobin, in order to quantitate red blood cell oxygen transport function in individuals who were diagnosed as hypothyroid, euthyroid, or hyperthyroid based on measurements of thyroxine (T4), triiodothyronine (T3), thyrotropin (TSH), and their clinical status. Hypothyroid (mean T4 2.8 microgram/dl, T3 49 ng/dl, TSH 37 microU/ml) and hyperthyroid (mean T4 14 microgram/dl, T3 271 ng/dl, TSH less than 0.7 microU/ml) patients had normal red cell 2,3-DPG and ATP levels and normal P50 values in vitro. The known changes in oxygen consumption produced by alterations in thyroid hormone levels in patients with hypothyroidism or hyperthyroidism did not affect red blood cell oxygen transport function.