Secondary adrenal insufficiency is adrenal hypofunction due to a lack of adrenocorticotropic hormone (ACTH). Symptoms are the same as for Addison disease
(See also Overview of Adrenal Function.)
Secondary adrenal insufficiency may occur in
Panhypopituitarism
Isolated failure of adrenocorticotropic hormone (ACTH) production
Patients receiving corticosteroids (by any route, including high doses of inhaled, intra-articular, or topical corticosteroids)
Patients who have stopped taking corticosteroids
Inadequate ACTH can also result from failure of the hypothalamus to stimulate pituitary ACTH production, which is sometimes called tertiary adrenal insufficiency.
Panhypopituitarism may occur secondary to pituitary tumors, various other tumors, granulomas, and, rarely, infection or trauma that destroys pituitary tissue. Especially in children and adolescents, but also in adults, panhypopituitarism may occur secondary to a craniopharyngioma.
Patients receiving corticosteroids for > 4 weeks may have insufficient ACTH secretion during metabolic stress to stimulate the adrenals to produce adequate quantities of corticosteroids, or they may have atrophic adrenals that are unresponsive to ACTH. These problems may persist for up to 1 year after corticosteroid treatment is stopped when the indication for their use is past, and may require reinstitution of treatment during periods of stress for an indeterminate period of time.
Symptoms and Signs of Secondary Adrenal Insufficiency
Symptoms and signs are similar to those of Addison disease and include fatigue, weakness, weight loss, nausea, vomiting, and diarrhea. Differentiating clinical or general laboratory features include the absence of hyperpigmentation and relatively normal electrolyte and BUN (blood urea nitrogen) levels. Hyponatremia, if it occurs, is usually dilutional.
Patients with panhypopituitarism have depressed thyroid and gonadal function and sometimes hypoglycemia. Coma may supervene when symptomatic secondary adrenal insufficiency occurs.
Diagnosis of Secondary Adrenal Insufficiency
Serum cortisol
Serum adrenocorticotropic hormone (ACTH)
ACTH stimulation testing
Central nervous system imaging
Tests to differentiate primary and secondary adrenal insufficiency are discussed under Addison disease. Patients with confirmed secondary adrenal insufficiency (see table Confirmatory Serum Testing for Secondary Adrenal Insufficiency) should have CT or MRI of the brain to rule out a pituitary tumor or pituitary atrophy.
Adequacy of the hypothalamic-pituitary-adrenal axis> 20 mcg/dL (> 552 nmol/L); specific levels vary somewhat depending on the laboratory assay in use.
cortisol in such patients may rise normally in response to the higher dose.
An insulin stress test to induce hypoglycemia and a rise in cortisol is the standard for testing integrity of the hypothalamic-pituitary-adrenal axis in many centers, but careful monitoring is required to avoid severe prolonged hypoglycemia. The test is contraindicated in patients with known or possible seizures, or ischemic heart disease, and it is not recommended in patients with suspected severe adrenal insufficiency.
Treatment of Secondary Adrenal Insufficiency
Dose increase during intercurrent illness
Glucocorticoid replacement is similar to that described for Addison diseasecortisol) is given in 2 or 3 divided doses with a typical total daily dose of 15 to 20 mg. One regimen gives half the total in the morning, and the remaining half split between lunchtime and early evening (eg, 10 mg, 5 mg, 5 mg). Others give two-thirds in the morning and one-third in the evening. Doses immediately before bed should generally be avoided because they may cause insomnia.
During acute febrile illness or after trauma, patients receiving corticosteroids for nonendocrine disorders may require supplemental doses to augment their endogenous hydrocortisone production.
In panhypopituitarism, other pituitary deficiencies should be treated appropriately.
Key Points
Secondary adrenal insufficiency involves adrenocorticotropic hormone (ACTH) deficiency due to pituitary or, less often, hypothalamic causes (including suppression by long-term corticosteroid use).
Other endocrine deficiencies (eg, hypothyroidism, growth hormone deficiency) may coexist.
Unlike in Addison disease, hyperpigmentation does not occur, and serum sodium and potassium levels are relatively normal.
ACTH and cortisol levels both are low.
