Some studies on the natural history of Graves' orbitopathy: increase in orbital fat is a rather late phenomenon

Abstract

AimTo describe volumes of orbital fat (FV) and extraocular muscles (MV) in Graves' orbitopathy (GO) as a function of the duration of GO.Patientsi) Cross-sectional survey among 95 consecutive patients with untreated GO who had been referred to the combined thyroid–eye clinics of our university hospital. ii) Longitudinal survey among 39 of the 95 patients who did not receive any therapeutic intervention and were followed for 1 year.MethodsA computed tomography (CT)-based and well-validated method for calculating orbital soft tissues. In order to neutralize sex differences, results are expressed as ratios of FV:orbital volume (OV) and MV:OV.Resultsi) Patients with GO duration of >1 year had greater FV:OV (0.65 vs 0.55, P=0.004), similar MV:OV (0.22 vs 0.21, not significant (NS)), and more proptosis (22 mm vs 21 mm, P=0.03) as compared to those with shorter duration. ii) As compared to baseline, after 1 year, FV:OV had increased (0.56 vs 0.63, P=0.000), MV:OV had not changed (0.19 vs 0.19, NS), proptosis was higher (20 mm vs 21 mm, P=0.003), and clinical activity scores had become lower (2 vs 1, P=0.02) (median values).ConclusionCT images show that a longer duration of GO is associated with a higher orbital FV. Extraocular MV, however, is not associated with GO duration; rather, it is related to the severity of GO.