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ABSTRACT
Adrenal insufficiency is characterised by inadequate glucocorticoid production owing to destruction of the adrenal cortex or lack of adrenocorticotropic hormone stimulation. In primary adrenal insufficiency, lack of mineralocorticoids is also a feature. Patients can present with an insidious onset of symptoms, or acutely in adrenal crisis, which requires prompt recognition and treatment. Chronic glucocorticoid therapy is the most common cause of adrenal insufficiency. The diagnosis of adrenal insufficiency is made by demonstrating low basal and/or stimulated serum cortisol and should be followed by appropriate investigations to establish the underlying aetiology. Maintenance glucocorticoid replacement is usually given as a twice or thrice daily hydrocortisone preparation. Patients with primary adrenal insufficiency also require mineralocorticoid. Regular monitoring for features of underand over- replacement is essential during follow-up. Patient education is a key feature of management of this condition.
Introduction
The adrenal cortex secretes the essential steroid hormones, cortisol and aldosterone, under the control of pituitary adrenocorticotropic hormone (ACTH), angiotensin II and plasma potassium. The most frequent cause of adrenal insufficiency is exogenous steroid use. Up to 2.5% of the population are taking such steroid medications for inflammatory or immune-mediated conditions.1 These individuals are vulnerable to steroid deficiency if the medication is stopped suddenly. ACTH deficiency (secondary adrenal insufficiency) as a result of pituitary tumours, infiltrative diseases, head injury or congenital hypopituitarism is the next most frequent cause, present in around 1 per 3,000 individuals.2 High dose opiates, which frequently induce hypogonadotropic hypogonadism, are also increasingly recognised as a cause of hypothalamic-pituitary-adrenal (HPA) suppression.3 By comparison, primary adrenal insufficiency is rare, with a prevalence of 1 in 8,000 people.4 In developed nations, an autoimmune attack directed against the adrenal steroidogenic enzymes (predominantly 21-hydroxylase)5 accounts for about 85% of cases. Around 60% of patients with autoimmune Addison's disease have an additional autoimmune condition, most frequently autoimmune thyroid disease or type 1 diabetes.6 In developing countries, tuberculosis, disseminated fungal infections and HIV remain significant causes of primary adrenal failure. In primary adrenal insufficiency, secretion of both cortisol and aldosterone is lost, whereas in secondary adrenal failure, or adrenal insufficiency caused by exogenous steroids, aldosterone secretion is largely intact.
Presentation of adrenal insufficiency
The clinical presentation depends on the tempo and extent of the loss of adrenal function. Common features...