Isolated corticotroph insufficiency associated to myasthenia gravis.

Myasthenia gravis, a neuromuscular junction autoimmune disease, may be associated to glandular autoimmune diseases such as adrenalitis. We report here the association of myasthenia gravis with a rare cause of adrenocortical deficiency, i.e. isolated corticotroph deficiency. The patient suffered from myasthenia gravis for 5 yr when she reported increased asthenia. Basal cortisol and ACTH levels were low. Metyrapone failed to increase ACTH and 11-desoxycortisol. Corticotropin-releasing hormone or tetracosactide failed to increase normally the cortisol levels. No other endocrine dysfunction or autoimmune disease could be detected. This observation enlarges the spectrum of endocrine diseases associated to myasthenia gravis and strengthens the need for careful endocrine examination.