The qRT-PCR analysis revealed significantly downregulated TGF-β (Tgfb1) and SOX9 (Sox9) and upregulated collagen X (Col10a1) mRNA, which is relevant to our histomorphology appearance, in the mandibular condylar cartilage of the IH group compared to that in the N group. Here, TGFB1 is linked to isolated hemihyperplasia.