Adrenocorticotrophic hormone (ACTH)

  • ACTH is released by the pituitary, a part of the Hypothalamic-Pituitary-Adrenal Axis (HPA Axis)

  • ACTH stimulates the adrenal glands (situated on top of the kidneys) to release the hormone cortisol.

  • Cortisol is a steroid stress hormone and is used in every cell of the body. It is essential for life.

  • When the pituitary is damaged, the feedback loop of the HPA axis can be damaged too, meaning the adrenal glands are not stimulated to release enough, or any cortisol.

  • ACTH deficiency is more commonly known as secondary adrenal insufficiency - the adrenal insufficiency is secondary to a problem in the pituitary. You may also hear it described as secondary Addison’s, hypoadrenalism or hypocorticolism.

 

Testing for ACTH Deficiency

  • Insulin Tolerance Test (ITT) also called Insulin Stress Test is the “gold standard” test. The test involves lowering blood glucose with the hormone insulin and measuring through blood samples how much cortisol is produced from the adrenal glands in response to that stress on the body. The hypoglycaemia is sensed at the hypothalamus so this tests the integrity of the whole axis. There are some contraindications to this and so you may be offered a different test if required.

  • Metyrapone test –an alternative where an Insulin Tolerance Test (ITT) is contraindicated.

    For this test you spend the night in hospital. At midnight you’re given a tablet containing Metryrapone along with a snack. In the morning, you will have a blood test between 8 am and 9 am to test the response of your HPA axis.

  • Glucagon stress test – an alternative where an Insulin Tolerance Test (ITT) is contraindicated.

    For this test you’re in the unit for the day from 9 am. You’ll have a cannula (a small needle) inserted into a vein in your arm. You’ll have blood tests before and at intervals after being given an injection of glucagon. The blood tests measure the response of your HPA axis and also your Growth Hormone.

Testing Adrenal gland function

You may be offered this test to see if your Adrenal glands can release the hormone Cortisol when stimulated. In many patients it can give information that is almost as reliable as an insulin or glucagon stress test. It is safer, quicker, more available and reproducible

Short Synacthen test – a synthetic form of ACTH is given to you via an injection. The response of your adrenal glands is then measured via a blood test. It therefore does not test the whole axis, but this does not matter in most cases, the information can still be useful.

Hormone replacement for ACTH deficiency

  • You will be given a cortisol replacement medication, rather than ACTH.

  • This is a steroid known as a glucocorticoid.

  • You may be given tablets such as Hydrocortisone or Prednisolone and it is vital you take these at the times directed by your endocrinologist.

  • Your cortisol levels will be monitored through blood tests. Your endocrinologist may ask you to come in to have a cortisol day curve if you are on Hydrocortisone. This is where you have blood tests at specific times through the day to check your cortisol replacement is correct. This is usually 9 am, 12 noon and 3 pm. If you are taking prednisolone you might be asked to do an 8 hour post-dose prednisolone level at some clinical centres.

  • Symptoms of low cortisol are wide ranging and may include weakness, dizziness, drowsiness, unsteadiness, headache, nausea, vomiting and diarrhoea.

Be safe

If you have been diagnosed with ACTH deficiency it is important you learn how to keep yourself safe and avoid a life-threatening lack of cortisol known as adrenal crisis.

Keeping Safe with Adrenal Insufficiency