Erythroid hyperplasia in the bone marrow is a response of the erythroid series to erythropoietin stimulation. These stimuli include hypoxemia (e.g., chronic, obstructive pulmonary disease), anemia less than 7 gm/ dl, a left-shifted oxygen dissociation curve (e.g., carbon monoxide poisoning), a bleed more than 5 to 7 days, and testosterone. Anemia of chronic disease, thalassemia minor, and iron deficiency have problems in hemoglobin synthesis, so these would not be expected to have a reticulocyte response. In chronic renal disease, there is a decreased concentration of erythropoietin, which results in a normocytic anemia and no reticulocyte response. Ref - Harrison's internal medicine 20e pg 391, 391f, 684, 696