Potential role for retinoic acid in patients with Cushing's disease

Context: Cushing's disease, i.e. cortisol excess due to an ACTH-secreting pituitary adenoma, is a rare disorder with considerable morbidity and mortality but no satisfactory medical treatment as yet. Experimental data have recently shown that retinoic acid restrains ACTH secretion by tumoral corticotropes. Objective: Our objective was to evaluate the efficacy and safety profile of retinoic acid treatment in patients with Cushing's disease. Design: This is a prospective, multicenter study. Seven patients with Cushing's disease (three men, four postmenopausal women) were started on 10 mg retinoic acid daily and dosage increased up to 80 mg daily for 6-12 months. ACTH, urinary free cortisol (UFC), and serum cortisol as well as clinical features of hypercortisolism and possible side effects of retinoic acid were evaluated at baseline, during retinoic acid administration, and after drug withdrawal. Results: A marked decrease in UFC levels was observed in five patients; mean UFC levels on retinoic acid were 22-73% of baseline values and normalization in UFC was achieved in three patients. Plasma ACTH decreased in the first month of treatment and then returned to pretreatment levels in responsive patients whereas no clear-cut pattern could be detected for serum cortisol. Blood pressure, glycemia, and signs of hypercortisolism, e.g. body weight and facial plethora, were ameliorated to a variable extent on treatment. Patients reported only mild adverse effects, e.g. xerophthalmia and arthralgias. Conclusions: Long-term treatment with retinoic acid proved beneficial and well tolerated in five of seven patients with Cushing's disease. This represents a novel, promising approach to medical treatment in Cushing's disease.