Because T2D patients is accompanied by an increased asprosin level, the lack of an association between asprosin and various metabolic parameters in PCOS patients suggests the mechanisms underlying glucose/insulin dysregulation in PCOS and T2D are distinct, and the interplay of irisin, asprosin, and other endocrine hormones could be key to the manifestation of distinct metabolic profiles in PCOS and T2D patients. Here, FNDC5 is linked to type 2 diabetes mellitus.