Circulating GnRH, FSH, and LH Levels in Keratoconus and Down Syndrome: A Cross-Sectional Comparison

Down syndrome (DS) is a common genetic disorder that has been strongly associated with keratoconus (KC). However, the underlying mechanism linking these conditions remains unexplored. KC is a corneal disorder characterized by corneal steepening, thinning, and scarring. The primary objective of this study was to determine the role of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in the context of DS and KC. A total of 58 healthy (29 male, 29 female), 227 KC (167 male, 60 female), and 80 DS participants (44 male, 36 female) were recruited. Hormone levels from plasma were analyzed using enzyme-linked immunosorbent assays, and differences between disease status, sex, and age were examined. GnRH was reduced in KC compared to healthy and DS participants, particularly in males. In contrast, FSH was elevated across both sexes in DS participants compared to healthy and KC participants. LH was also significantly elevated in DS, particularly among females and among participants from 30–45 age group, mirroring the pattern seen for FSH. These cross-sectional findings reveal distinct hormonal patterns across KC and DS cohorts while providing novel descriptive data on hypothalamic–pituitary–gonadal axis hormones. Further studies are warranted to determine the relationship between gonadotropins and the phenotypic manifestations in these populations.