INCREASED cellular metabolism with excessive catabolism of body protein and loss of weight is a basic factor in the pathophysiologic aspects of hyperthyroidism. In patients with hyperthyroidism gain of weight signifies clinical improvement. Failure to gain weight during the period of preoperative preparation is associated with increased operatve morbidity and mortalty. 1 Attention has recently been directed to the significance of hemoglobin deficiency in the depletion of protein associated with loss of weight in many types of chronic illness. 2 In such progressive depletion of protein the deficit in the total mass of circulating red blood cells may be masked by a constriction of the volume of plasma and can be determined only by studies of the volume of blood. The routine laboratory procedures of determinations of hematocrit percentage, red blood cell counts and determinations of hemoglobin are frequently inadequate in determining the true degree of anemia in debilitated patients.