To the Editor.
—The article entitled "Anemia and Secondary Hyperparathyroidism" in the November Archives (138:1650-1652, 1978) reports that subtotal parathyroidectomy resulted in a substantial increase of mean hematocrit value and hemoglobin level, but the precise mechanism was unknown. The reason the mechanism was unknown is because the authors did not do the proper studies.Anemia is, by definition, a reduction in the RBC mass. It is most likely that the changes the authors observed were changes of hemodilution. The article should not have been published without showing a change in RBC mass.