Endocrine Abstracts

Introduction: Isolated ACTH deficiency (IAD) is a rare entity characterized by secondary adrenal insufficiency with low levels of serum cortisol, decreased production of ACTH, adequate secretion of other pituitary hormones and normal pituitary structure on radioimaging. Due to the rarity of its occurrence the prevalence of IAD as a cause of secondary adrenal insufficiency has not been determined. To our knowledge 200 cases are described in the literature. Impairment of GH secretion has been noted in 20–30% of patients with IAD which is normalized after glucocorticoid replacement.

Case report: This is the case of a 56 y/o female patient initially referred to the endocrine clinic complaining of tiredness, fatigue, weakness, and an elevated TSH level. She reported a history of a previous episode of syncope 10 years before evaluation and three episodes of near syncope 2 years later associated to tiredness, weakness and sweating. Physical exam was unremarkable and she was initially treated for hypothyroidism with levothyroxine. In the subsequent visits the patient complained of worsening tiredness associated to dizziness, nausea and occasional vomiting. A low serum cortisol level with a low ACTH level suggested the diagnosis of secondary adrenal insufficiency. An ACTH stimulation test showed no rise in serum cortisol from baseline. Complete evaluation of anterior pituitary hormones was unremarkable. A pituitary MRI was normal. An insulin tolerance test demonstrated ACTH and GH deficiency. Treatment was initiated with low dose hydrocortisone and symptoms resolved. After 8 months of treatment a glucagon stimulation test revealed persistent ACTH deficiency but GH secretion normalized.

Conclusion: IAD is a rare cause of secondary adrenal insufficiency that can present with nonspecific symptoms and could be potentially fatal in an acute stress period. Prompt recognition is essential to decrease morbidity and mortality. Symptoms of adrenal insufficiency and GH deficiency may overlap therefore it is important to recognize that transient GH deficiency may present with IAD to avoid unnecessary exposure to GH replacement therapy and its potential adverse effects and high cost.