High dose intravenous methylprednisolone pulse therapy causes transient increase of serum calcium and phosphate levels.

: High and very high doses of intravenous methylprednisolone (IVMP) administered in pulses are the first-line treatment for active, moderateto- severe, as well as sight-threatening Graves' orbitopathy (GO). However, glucocorticoid therapy is associated with side effects, among others, it affects bone metabolism. AIM: The aim of study was to assess the acute effects of high and very high doses of IVMP on calcium (Ca) and phosphate (P) balance in euthyroid patients with moderate-to-severe GO and sight-threatening GO due to dysthyroid optic neuropathy (DON). MATERIALS AND METHODS: Thirty-six patients with active, moderate-tosevere GO were treated with twelve once-weekly pulses (with cumulative dose of 4.5 g IVMP) and 11 patients with DON received 3 intravenous pulses of 1.0 g IVMP on three consecutive days. We measured serum levels of Ca and P at baseline and on the following days after the beginning of the IVMP therapy. RESULTS: We observed a significant increase in serum Ca level on the next day after the 1st IVMP pulse both in patients with moderate-tosevere GO and with DON. Then, on the day 3, the decrease of serum Ca was noticed. In patients with moderate-to-severe GO, on the day 2 serum P showed a significant increase and then, it returned to basal level on the day 3. CONCLUSIONS: We observed a significant increase in serum Ca level on the next day after the 1st IVMP pulse both in patients with moderate-tosevere GO and with DON. Then, on the day 3, the decrease of serum Ca was noticed. In patients with moderate-to-severe GO, on the day 2 serum P showed a significant increase and then, it returned to basal level on the day 3.