Efficacy and safety of a 30-day methylprednisolone treatment protocol for subacute thyroiditis: a prospective study

Objective: The optimal corticosteroid treatment regimen for subacute thyroiditis has not yet been established. To avoid side-effects, tapering of the initial dose of corticosteroid is recommended. With reducing dose, the symptoms can recur. Design: In a prospective clinical study, a 30-day methylprednisolone (MPSL) treatment protocol with a starting dose of 24 mg/day and tapered by 4 mg every 5 days was assessed for effectiveness and safety regarding possible adrenal insufficiency. Methods: Fifty-nine patients with subacute thyroiditis were included. At visit 1, after establishing the diagnosis, a short stimulation ACTH test was performed and methylprednisolone treatment prescribed. At visit 2 (40±5 days after visit 1), clinical, laboratory (including short stimulation ACTH test), and ultrasound evaluation were repeated. Results: Forty-eight patients (81.4%) were cured by the prescribed protocol, having significantly lower cortisol levels after stimulation at visit 1 than patients who were not cured (mean, 674.9 nmol/L and 764.0 nmol/L, respectively, p=0.012). Seven patients (12.3%) developed adrenal insufficiency; this group had significantly lower cortisol level after stimulation at visit 1 than patients who did not (mean, 561.5 nmol/L and 704.7 nmol/L, respectively, p=0.005). Using stimulated cortisol level at visit 1 as the explanatory variable, logistic models were optimized to determine treatment efficacy (AUC=0.745, optimal threshold 729 nmol/L, specificity 71%, sensitivity 73%), and adrenal function (AUC=0.861, optimal threshold 629 nmol/L, specificity 73%, sensitivity 100%). Conclusions: The described protocol was efficient for more than 80% of patients. Using this protocol, the corticosteroid treatment interval is shorter than proposed in current guidelines.