Secondary: lack of production of ACTH by the pituitary gland

Tertiary: lack of CRH secretion by the hypothalamus

Aetiology

• Iatrogenic (excess exogenous steroid) - inhibit CRH production and ACTH production, adrenal gland becomes atrophied and is unable to produce cortisol even acutely when ACTH is given endogenously
• Pituitary/hypothalamic disorders - tumours, surgery and radiotherapy

Clinical features

Similar to Addison's except:

• Skin pale (no ↑ ACTH)
• Aldosterone production intact (regulated by RAAS)
  • No hypertension

Investigations

• Insulin tolerance test
• CRH stimulation test
• MRI

Management

• Treat with hydrocortisone replacement (fludrocortisone unnecessary)