Role of Thyroxine in the Development of Keratoconus.

PURPOSE: Keratoconus (KC) is a corneal ectasia whose pathophysiology is still mostly unknown. We investigated whether thyroid gland dysfunction (TGD) is associated with the development of KC.

METHODS

We first conducted an epidemiological study, examining the prevalence of TGD among patients with KC. Then, we compared tear thyroxine (T4) in TGD and immunohistochemical staining of its receptors (T4Rs) between patients with KC and controls. The significance of T4 for corneal metabolism was studied in organotypic tissue cultures from monkey corneas.

RESULTS

We found that TGD prevalence among patients with KC is 13.6%, which is higher than its prevalence in the general population (about 2%). Tear T4 was higher in KC, and keratocyte T4Rs were elevated in KC compared with controls. Furthermore, core proteins such as collagen and cytokeratins were equally altered both in KC and in the cultured corneas substituted with T4.

CONCLUSIONS

Our data implicate a crucial role of T4 in KC pathophysiology, which is most likely mediated by T4Rs.