SAT-046 Insulin-Like Growth Factor and Fibroblast Growth Factor 21 in Men with Klinefelter Syndrome

Background: Men with 47, XXY Klinefelter syndrome (KS) commonly present with obesity, metabolic disorders, and insulin insensitivity. The insulin-like growth factor (IGF) system has pleiotropic effects including regulation of glucose metabolism. Fibroblast growth factor 21 (FGF21) is associated with weight loss and favourable metabolic changes, but patients with obesity or type 2 diabetes might be resistant to this effect despite presenting with increased levels. Aim: To describe levels of components in the IGF system and FGF21 among men with KS, either treated or not treated with testosterone supplementation therapy (TT), in comparison with control males. Methods: A total of 66 men with KS were included, 33 without current TT and 33 with current TT. A control group of 70 healthy age-matched males were included. Serum levels of insulin-like growth factor 1 (IGF-1), insulin-like growth factor-binding protein 3 (IGFBP3), pregnancy-associated plasma protein A (PAPP-A), FGF21, and fibroblast activation protein (FAP) were compared between the three groups applying the Kruskal-Wallis test. Results: Levels of (IGF-1 µg/L) were not different between the groups (median (25-75 %), untreated KS 162 (140-201.5), treated KS 165 (128.5-215), controls 176.5 (150.8-214.5), p=0.5). Similarly, FGF21 levels (ng/L) were comparable between the groups (median (25-75 %), untreated KS 84.7 (53.3-217.6), treated KS 97.2 (56.4-224.8), controls 100.3 (66.0-191.0), p=0.9). Levels of IGFBP3, PAPP-A and FAP were also found to be comparable between the groups (p≥0.2). Conclusion: This was the first study investigating FGF21 in men with KS. Our results indicate that regulation of the IGF-1 system and levels of FGF21 are not altered in men with KS compared with age-matched controls, and that TT in men with KS does not affect these systems.