Which condition is primarily associated with normocytic anemia?

Normocytic anemia is characterized by the presence of red blood cells that are normal in size but reduced in number. Chronic kidney disease, particularly in its end-stage renal disease (ESRD), is primarily associated with this type of anemia. The kidneys play a crucial role in the production of erythropoietin, a hormone that stimulates the bone marrow to produce red blood cells. In ESRD, the decline in kidney function leads to decreased production of erythropoietin, resulting in insufficient red blood cell production while the cells that are produced remain normocytic.

In contrast, vitamin B12 deficiency typically leads to macrocytic anemia, where red blood cells are larger than normal due to impaired DNA synthesis. Iron deficiency anemia is usually microcytic, characterized by smaller red blood cells due to insufficient iron necessary for hemoglobin production. Hemolytic anemia can present as normocytic in some cases, but it is primarily defined by the destruction of red blood cells, which is a distinct mechanism when compared to the anemia associated with chronic kidney disease. Thus, among the options presented, chronic kidney disease is most directly linked to normocytic anemia due to its impact on erythropoietin production.