Ectopic ACTH

This is the production of adrenocorticotrophic hormone (ACTH) from a source other than the anterior part of the pituitary gland.

This phenomenon is usually associated with a small cell carcinoma of the bronchus. Less common causes include thymic tumours, pancreatic adenocarcinoma, bronchial carcinoid.

Presentation:

• Cushingoid features may be present if the tumour is slow growing
• features generally include:
  • generalized muscle weakness
  • mental abnormality
  • oedema (fluid retention)
  • diabetes
  • skin hyperpigmentation
  • hypokalaemic alkalosis
• although metastasis to the adrenals often occurs with bronchogenic carcinoma a hormonal deficiency due to replacement is very unusual

Investigation:

• no increased in steroid metabolites after metyrapone administration
• no suppression of cortisol levels after dexamethasone administration

Treatment:

• tumour resection or adrenalectomy
• medical management includes the use of drugs such as the adrenolytic mitotane and aminoglutethimide