Prolonged adrenal insufficiency following discontinuation of osilodrostat treatment for intense hypercortisolism

The cases of 3 patients with Cushing's disease who developed long-term adrenal insufficiency after discontinuation of prolonged osilodrostat therapy were recently described for the first time. We report 2 additional cases of persistent prolonged adrenal insufficiency after discontinuation of osilodrostat treatment for intense hypercortisolism due to Cushing's disease and ectopic ACTH syndrome. In addition, we show for that adrenal insufficiency in these patients was associated with low/normal 11-deoxycortisol concentrations despite high plasma ACTH concentrations. These results suggest that CYP11B1 is not the only target of osilodrostat and that, in vivo, osilodrostat has other prolonged and strong inhibitory effect on adrenal steroidogenesis upstream of CYP11B1. Knowledge of this remnant effect is important for the care of patients with Cushing's syndrome treated with osilodrostat. Further studies are needed to clarify the frequency and the mechanisms of this remnant effect.