Adrenal insufficiency is defined by the impaired synthesis and release of adrenocortical hormones. It is classified based upon the mechanism:
- Primary adrenal insufficiency, also known as Addison's disease, results from disease intrinsic to the adrenal cortex (table 1).
- Central adrenal insufficiency is caused by impaired production or action of adrenocorticotropic hormone (ACTH). It can be caused by several mechanisms:
- Secondary adrenal insufficiency results from pituitary disease impairing release of adrenocorticotropic hormone (ACTH). In addition, unresponsiveness of end-organs to adrenocortical hormones is classified as secondary adrenal insufficiency because this presents in a similar manner as diseases caused by adrenocorticotropic hormone (ACTH) deficiencies (table 2).
- Tertiary adrenal insufficiency results from the impaired release or effect of corticotropin releasing hormone (CRH) from the hypothalamus (table 3).
Clinical findings of children with adrenal insufficiency include fatigue and gastrointestinal complaints of nausea and vomiting. Additional symptoms can be categorized based upon the specific hormones affected (table 4). Signs of mineralocorticoid deficiency (hypotension, dehydration, and electrolyte abnormalities) are often observed in patients with primary adrenal insufficiency.
The most common cause of adrenal insufficiency in infants is classic congenital adrenal hyperplasia, which is discussed separately. (See "Treatment of classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency in infants and children".)