Association of Elevated Thyroid-Stimulating Hormone With Structural Progression in Keratoconus

The aim of this study was to evaluate whether serum thyroid-stimulating hormone (TSH), total T3, and free T4 levels are associated with tomographically confirmed structural progression in keratoconus.

In a prospective observational cohort, 133 eyes from 74 individuals were classified into progressive keratoconus (n = 53), stable keratoconus (n = 28), and healthy control eyes (n = 52). Progression was defined as a ≥1.0 D increase in maximum keratometry (Kmax) over 12 months. Corneal imaging and serum hormone assays (TSH, T3, T4) were performed at baseline. Group comparisons used ANOVA with Tukey post hoc testing. Pearson correlation assessed associations between hormone levels and structural parameters.

The progressive group demonstrated significantly higher TSH levels (1.96 ± 0.83 mU/mL) compared with controls (1.47 ± 0.57 mU/mL; P < 0.05); stable group values were intermediate. No differences were found for T3 or T4. Correlations between TSH and steep keratometry (K2) (r = +0.27; P < 0.05) and between TSH and thinnest pachymetry (r = -0.21; P < 0.05) were statistically significant. No correlation was observed between TSH and minimum epithelial thickness, or with T3/T4 levels.

Elevated TSH is associated with structural progression markers in keratoconus, suggesting a systemic thyroid contribution to disease evolution. While causality is not established, these findings support endocrine screening in early or progressive keratoconus cases and warrant further mechanistic investigation.