RETN and polycystic ovary syndrome: The hypermethylation of tumor necrosis factor (TNF) and the hypomethylation of aldo-keto reductase 1 C3 (AKR1C3), calcium-sensing receptor (CASR), growth hormone-releasing hormone receptor (GHRHR), resistin (RETN) and mastermind-like domain 1 (MAMLD1) lead to hyperandrogenism, causing the hormone disbalance that is crucial for the pathogenesis of PCOS [66].