Fig. 1
Schematic diagram shows possible mechanisms of calcium regulatory pathway and intestinal calcium absorption in thalassemia. Reduction of calcium-regulating hormones, i.e., parathyroid hormone (PTH), calcitonin, and 1,25(OH)2D3, in thalassemia leads to a decrease in the intestinal calcium absorption. Inset The decreased intestinal calcium absorption in thalassemia is due to downregulation of transcellular calcium transport-related proteins (TRPV5/6, PMCA1b, and NCX1). The possible mechanism may also involve downregulation of NKA and tight junction proteins, such as claudins, thereby compromising the paracellular calcium transport (for details, please see text). PVALB, parvalbumin; CaBP, calcium-binding proteins (e.g., calbindin-D9k); Cav1.3, voltage-dependent calcium channel 1.3