Why do I need a synacthen Test?

Posted , 10 users are following.

There is occasional reference in this and another PMR forum about the need for prednisone users to request a synacthen test. I'm not clear as to why.

A definition of the test that I found on the net says this:

"Synacthen is a manufactured drug that acts like adrenocorticotrophic hormone (ACTH) by stimulating the adrenal gland to produce more cortisol. By measuring the rise in cortisol in the blood the doctor can see if the adrenal glands are secreting normal amounts of cortisol."

However, it is my understanding that prednisone users have adrenal glands that are NOT secreting normal amounts of cortisol. So...of what value is the test?

Putting my question on a more personal level:- I am now at the 6.5 mg prednisone level daily.

That is just below the magic 7.0-7.5 level that they say is normal cortisol production. My adrenals should be kicking in a half mg or so to keep me on an even keel. Are they?

Will a synacthen test answer that question?

Hope this posting is not too technical. Any light that you can shine on this subject would be appreciated.

0 likes, 5 replies

5 Replies

  • Posted

    The synacthen test, or synthetic ACTH stimulation test, is used to assess whether the adrenal glands would be able to respond to a stimulus and produce cortisol, the body's natural corticosteroid. During long term treatment with artificial corticosteroids at a dose above about 8mg prednisolone/prednisone the production of cortisol is suppressed because the complex feedback set-up in the body that governs the functioning of the HPA axis (hypothalamus, pituitary and adrenal glands) gets signals telling it there is already adequate corticosteroid present to allow the body to function properly and no more is required as excess corticosteroid, as we know, causes problems. Once the level of corticosteroid falls below that level, the adrenal glands must come out of hibernation and top up the oral dose to the level required for the body to function. This dose varies from person to person because some people absorb more of their oral dose than others, the bioavailability. In most people, when they reduce slowly, the adrenals recover and produce cortisol again. It is said to take at least a year after ceasing to take any pred before this function is reliable.

    However, in some people the adrenal glands do not wake up and so as the dose is reduced, the body is not topping up the requirement and slowly the person enters a state of secondary Addison's disease. In the event of a sudden excessive stress, the body is unable to produce the top-up and, where required, the excess spike of cortisol to allow the body to cope under stress. This may trigger an Addisonian crisis.

    It has generally been thought that, providing patients reduce their dose of pred slowly enough, the adrenal glands will come out of hibernation and produce cortisol. In fact, it is becoming apparent that more people than it is thought DON'T start to produce endogenous cortisol while reducing their pred dose. Down to about 2 or 3mg pred they may still be functioning well and not notice any problems although others may experience overwhelming fatigue as a sign that all is not well. One lady on the forums was at 2mg pred and felt fine. It just so happened her rheumy asked for a synacthen test and it was found she has no endogenous adrenal function at all. She is at an increased risk of an Addisonian crisis and could become seriously ill. The synacthen test showed her adrenal glands would not function. That is all that test shows really - that they cannot produce cortisol under their own steam, and that the patient requires a replacement therapy, usually with hydrocortisone but also sometimes with pred. In that case, the patient needs to be referred to an endocrinologist for expert assessment.

    Does that answer your question? If not, ask again.

    • Posted

      Please would someone with knowledge UK NHS tell me whether Patient, GP or Consultant is the one to initiate request for the test?

    • Posted

      Thanks for the detailed reply, Eileen.

      I'm going to have to study it carefully, but I'm sure I will have a question (or two).

    • Posted

      So, from what you're saying, I get that even if you're below the magic 7.0 to 7.5 pred level, when your own adrenals are expected to start contributing to the cause...they may not kick-in as expected.

      If you suspect that this is the case, a synacthen test might be called for.

      And, one of the symptoms of this condition is overwhelming fatigue.

      I get it now. Thank you, Elaine.

    • Posted

      Any of them - you can speak to your GP or your consultant about whether they think it might be appropriate. Then it depends on the CCG - in some places a GP may be able to request one directly, in others it may have to be the specialist unit. They are usually done at a hospital day clinic. If all else fails, you can ask for a referral to an endocrinologist.

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