Intravenous glucocorticoids (IVGC) remain first-line therapy for active thyroid eye disease (TED). This study aimed to (1) compare baseline biochemical characteristics between active and inactive TED and (2) evaluate clinical, metabolic, and immunological changes following high-dose IVGC therapy exceeding 4500 mg methylprednisolone.

54 patients with a documented baseline Clinical Activity Score (CAS) were included. Variables collected included demographics, smoking status, hereditary predisposition, thyroid status, diagnosis, and cumulative IVGC dose. Baseline differences between inactive (CAS < 3) and active (CAS ≥ 3) TED were analyzed using the Mann–Whitney U test. Paired clinical and biochemical changes before and after pulse-therapy were assessed using the Wilcoxon signed-rank test.

The cohort included 38 females (70%) and 16 males (30%), median age 54 years (IQR 43–62). 16 patients (30%) were smokers and 13 (24%) had hereditary thyroid predisposition. Median BMI was 27.7 kg/m² (IQR 22.6–32.3). Thyroid status comprised 32 euthyroid (59%), 14 hypothyroid (26%), and 8 hyperthyroid (15%) patients. Among 35 patients with a documented diagnosis, 33 (94%) had Graves’ disease and 2 (6%) Hashimoto’s thyroiditis. Overall, 42 patients (78%) had active TED and 12 (22%) were inactive; inactive patients had a mean CAS of 1.5 and mean severity of 1.08. Active TED was associated with higher serum sodium (140.5 vs. 138.9 mmol/L; p = 0.026) and higher cholesterol (5.29 vs. 4.53 mmol/L; p = 0.017), with no other significant differences. Among active patients with paired data (n = 24), mean CAS and severity before therapy were 3.71 and 1.96, respectively. Following IVGC treatment (median cumulative dose 6625 mg; range 3000–8500 mg), 21 patients (88%) achieved CAS < 3, while 3 (12%) remained active. Mean CAS improved to 1.88 and severity to 1.38. Biochemical changes included reduced LDL cholesterol (3.29 to 2.79 mmol/L; p = 0.040), increased GGT (18.8 to 22.6 U/L; p = 0.039), and decreased protein (70.3 to 66.5 g/L; p = 0.00037). ALT, AST, and glucose remained stable. TRAb declined markedly (17.6 to 7.58 IU/L; p = 0.0013). No treatment discontinuation occurred due to adverse events.

High-dose IVGC produced significant clinical, biochemical, and immunological improvements, including reductions in CAS, LDL cholesterol, and TRAb. The absence of safety-related treatment interruptions suggests that IVGC doses above 4500 mg can be safely administered in appropriately selected patients.