4th April 2024

Diagnosis

The signs and symptoms of Addison’s disease can be vague but a detailed history and examination, as well as simple blood tests such as urea and electrolytes, can raise suspicion. Some findings which are indicative of Addison’s disease include:

• Hyponatraemia and hyperkalaemia (due to low aldosterone levels)
• Hypoglycaemia (due to low cortisol)
• Uraemia
• Normocytic anaemia

If Addison’s disease is suspected a morning cortisol level should be taken and further investigations depending on the result:

• <83 nmol/L is highly suggestive of adrenal insufficiency
• >497 nmol/L makes adrenal insufficiency highly unlikely
• 83-497 nmol/L warrants further testing to determine if there is adrenal insufficiency

The diagnostic test for Addison’s disease is an ACTH suppression test, also called the short Synacthen test. This involves measuring baseline serum cortisol followed by administration of synthetic ACTH (Synacthen) to the patient after which cortisol levels are rechecked at 30- and 60-minute intervals. In an individual with healthy adrenal tissue, administration of ACTH will lead to a rise in cortisol but in Addison’s disease, the adrenal glands will not be able to mount a response. Cortisol levels below 497 nmol/L after synthetic ACTH indicate probable adrenal insufficiency and these patients will require further evaluation by an endocrinologist to confirm the diagnosis.