TGFB1 and isolated hemihyperplasia: In addition, BMP2, OPN and the vitamin D (1,25-dihydroxyvitamin D3) receptor (VDR) are also upregulated in renal specimens of IH patients; co-incubation of TGF-β1 and calcium significantly increased the expression levels of these factors in primary renal tubular epithelial cells (PRECs) of IH patients [15].