Effect of high-dose intravenous glucocorticoid therapy on serum thyroid hormone concentrations in type 2 amiodarone-induced thyrotoxicosis: an exploratory study

Purpose: Type 2 amiodarone-induced thyrotoxicosis (AIT2) is a form of drug-induced destructive thyroiditis, usually treated with oral glucocorticoids (oGCs). Our objective was to investigate the short-term effects of intravenous glucocorticoids (ivGCs) on serum thyroid hormone concentrations in patients with AIT2. Methods: Exploratory study of three naive AIT2 patients treated with iv methylprednisolone (two pulses of 400 mg with no interpulse oGCs), followed by oGCs, matched 1:3 with AIT2 patients treated with oGCs alone. Changes in serum thyroid hormone concentrations were evaluated in the short-term period (24 h and 7 days) and after a cumulative dosage of 400 and 800 mg equivalents of methylprednisolone; in addition, healing time and duration of exposure to GCs were calculated. Results: During the first 24 h of treatment, serum FT4 concentrations increased in ivGCs patients, and decreased in oGCs patients (+ 3.3% vs − 10.7%, respectively, p = 0.025). After 7 days, serum FT4 and FT3 concentrations decreased significantly in both groups, with no statistical difference between them (p = 0.439 for FT4 and p = 0.071 for FT3), even though the cumulative GCs dose was higher in ivGCs than in oGCs patients (800 mg vs 280 mg, p = 0.008). Furthermore, the iv administration of single 400 mg pulses of methylprednisolone resulted in a less significant decrease in serum thyroid hormone concentrations when compared to equivalent GCs doses fractionated in several consecutive days (p = 0.021 for FT4 and p = 0.052 for FT3). There were no significant differences in the healing time (p = 0.239) and duration of exposure to GCs (p = 0.099). Conclusions: High-dose ivGCs therapy does not offer advantages over standard oGCs therapy in the rapid, short-term control of AIT2.