Thyroid UK
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Synacthen Percentage Result?

Hi all,

Little bit of an odd question. Just wondering if anyone has had a synacthen test performed very recently where the result, i.e. has their cortisol increased enough, been calculated using a percentage formula? I have been told by an endocrinologist that this is how it is now done but he did not go into any further details or say what the percentage increase would need to be.

I had my synacthen test done about 7 years ago and as my increase always felt quite small I would like to calculate or look again at the result using this percentage formula.

Any help would be great. Thanks!

2 Replies

I imagine he is saying :

If the starting level of cortisol is, say, 200 nmol/L, and the response to the injection after 30 minutes is a cortisol level of 250 nmol/L then there has been a 25% rise. If his rulebook says a 25% rise is sufficient then tell the patient they are healthy and send them on their way.

If the starting level is 400 nmol/L and it rises to 500 nmol/L then that is also a 25% rise.

Obviously I have no idea what starting level they consider satisfactory, nor what percentage rise they are claiming is satisfactory. But I must admit I'm not impressed by this method, I think it will leave many people ill and untreated.

For more info on the short synacthen test (SST) and other endocrine testing, see this document, last updated in February 2017, so very up to date. The SST is described on page 68. It does NOT mention the percentage rise method of determining if there is a problem :


Thanks for the reply.

The way you describe it is how i envisioned it working too, i was just hoping someone may have experienced that new method and known what the percentage rise is deemed acceptable. As i said i was always a little sceptical about the way my result was accepted as fine so quickly and easily, although it may well be, and so thought it might be worth pursuing this new way of interpreting results just to be sure.

But having read the link you provided, which was really helpful, it looks like it's certainly not being used on a widespread basis. Makes me wonder if my endocrinologist just said that to keep me quiet. I'm not due to see him again for months but I'll have to be more assertive with him and ask for a full explanation of the percentage system he claims they now use. See if it's legit and he can give full details regarding it.

Thanks again for the help!

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