Adrenal cushing - ACTH independent cushing

Introduction to Adrenal Cushing (ACTH-independent Cushing)
Adrenocortical tumours producing cortisol are ACTH-independent, and denoted Adrenal Cushing or ACTH-independent Cushing. The reason is most often an adenoma although bilateral hyperplasia also occurs. In case of hormones produced in adrenocortical cancer it is usually cortisol, or immature steroids with similar effects as cortisol that is produced. An overview of diagnostics and treatment follows:

Background of Adrenal Cushing
Adrenocortical adenomas are rarely associated with an overt Cushing’s syndrome. However, lower secretion of cortisol leading to subclinical Cushing’s syndrome is more common than previously anticipated. The tumour is usually diagnosed after evaluation of an adrenal incidentaloma or in search for explanation of a suspected Cushing’s syndrome. In rare cases a bilateral hyperplasia is present. The usual associations with the more common and overt Mb Cushing may be present such as buffalo hump, central obesity, moon face, skin striae, muscle atrophy, diabetes mellitus and osteoporosis.

Diagnostics of Adrenal Cushing
The biochemical diagnosis is based on a pathological dexametasone suppression test in conjunction with a low ACTH level and findings of an adrenocortical tumour on imaging. A 24-hour acyclic cortisol curve is also confirmatory, preferably measured by using salivary cortisol. 24-hour urinary cortisol level is increased. In rare cases of bilateral hyperplasia adrenal venous sampling can be performed.

Treatment of Adrenal Cushing
The optimal treatment is adrenalectomy, preferably performed laparoscopically or retroperitoneoscopically. The patients are prone to develop infections and should have prophylaxis with antibiotics. Postoperatively there is a high risk for adrenal insufficiency, why substitution with cortisol should be given, usually lasting more than 6 months in a successive reducing dose.