Final answer:
The percentage of transferrin saturation is the parameter that decreases to indicate reduced availability of iron for erythropoiesis in Anemia of Chronic Disease.
Step-by-step explanation:
In the context of Anemia of Chronic Disease (ACD), the parameter that indicates the reduced availability of iron for erythropoiesis is the percentage of transferrin saturation. During ACD, the body's iron regulation system restricts the release of iron from storage even when the body requires it for red blood cell production, which results in lower transferrin saturation without an actual decrease in total body iron stores. Thus, in ACD, the level of serum ferritin, which reflects iron stores, usually remains normal or may even be elevated as part of the acute phase response. In contrast, serum iron (Serum FE) levels and the total iron-binding capacity (TIBC) may decrease but are less specific indicators of ACD compared to the % transferrin saturation.