Study helps explain prominence of brow fat in patients with thyroid-associated orbitopathy

The authors tested their hypothesis that brow enlargement in patients with thyroid-associated orbitopathy (TAO) occurs secondary to the autoimmune process in Graves’ disease and that the changes in the brow fat are histologically identical to those seen in orbital fat.

They prospectively compared orbital and fat histologies of patients with TAO to those of patients without known systemic disease. They found that the orbital and brow fat of patients with TAO displayed identical histologic changes, with an increase in fibrosis and fibrous septae compared to controls, and increased expression of insulin-like growth factor 1 receptor β (IGF-1Rβ) and thyroid-stimulating hormone receptor (TSHR).

Studies have shown that antibodies to TSHR are important in the pathogenesis of TAO and that immunoglobulins from these patients can also activate IGF-1Rβ, which leads to production of chemoattractants. Therefore, the authors conclude that expression of both TSHR and IGF-1Rβ in orbital and brow tissues further supports their role as putative markers in patients with Graves’ disease, and hope that targeted treatments to prevent the periorbital changes can be developed.