Synacthen test same as ACTH???

[LBM1953]

Can anyone tell me whether a Synacthen test is the same as an ACTH? Just had a conversation with Spire Hospitals and they said they were not the same....

[PMRpro Ambassador]

Suppose it depends on how you define it and what you mean.

ACTH is the natural product made in the body, not the test itself, they would just measure the level in blood if they did anything.

The synacthen test is a test done by administering synthetic (man-made) ACTH as part of a test. First they take a blood sample to measure basal cortisol levels and then give you an injection of the synacthen. This stimulates the adrenal glands to produce cortisol if they can. Then another blood sample is taken to see how well they have responded.

Who did you speak to at Spire?

[LBM1953 in reply to PMRpro]

Just someone in a chat room who couldn't tell me if they were the same so consulted and then said no they weren't. They do something called an ACTH test but not a Synacthen test so I guess that this simply tests the level of ACTH and therefore not much use to see how the adrenals react.

[PMRpro Ambassador in reply to LBM1953]

Whoever they asked doesn't appear to be that clear either - I think an ACTH test is actually an ACTH stimulation test and is the same as a synacthen test

medlineplus.gov/lab-tests/a...

[LBM1953 in reply to PMRpro]

That's what I thought but I didn't have sufficient knowledge to argue with him. I'll try again......

[LBM1953 in reply to LBM1953]

I think that they may be correct. The link that you sent me seems to confirm that an ACTH Test is different to an ACTH Stimulation Test, (as you say the latter is the same as a Synacthen Test). I think that an ACTH Test simply measure the amount of ACTH in the body. This is the extract:

Is there anything else I need to know about an ACTH test?

A test called an ACTH stimulation test is sometimes done instead of an ACTH test to diagnose Addison disease and hypopituitarism. An ACTH stimulation test is a blood test that measures cortisol levels before and after you've received an injection of ACTH (or Synacthen - my words).

[PMRpro Ambassador in reply to LBM1953]

Possibly - but seems a bit pathetic for them to do the easy one. Even your GP should be able to order that, Free ...

[LBM1953 in reply to PMRpro]

GP said they cannot order a Synacthen test (when I asked her). ACTH test wasn't discussed. No worries, I don't think I need one, just ascertaining all the info just in case I think I do. Many Thanks. LBM2953

[PMRpro Ambassador in reply to LBM1953]

No - I meant the simple cortisol test. That is just a simple morning blood sample.

[LBM1953 in reply to PMRpro]

Okee dokee...😃👍

[PMRpro Ambassador in reply to LBM1953]

And the basal cortisol is good enough to show definite adrenal insufficiency (under 100) and definite normal (over 450). Inbetween is equivocal and with an ordinary patient would mean a request for a synacthen test for clarification.

However - when in pred you are unlikely to get normal cortisol levels until a very low dose, below 3mg. So the morning cortisol level will show if there is any return of function and you can get a clue to how much from the level. Do you see what I'm getting at?

[LBM1953 in reply to PMRpro]

Yep. I'm presently transitioning from 4 to 3 so I'll keep an eye on it and speak to my GP at some point (she is great and very accommodating)....

[PMRpro Ambassador in reply to LBM1953]

If it were me, I think I would ask if she will do a basal cortisol for you now and then you can see where it goes as you reduce the pred further, Some people start to recover sooner than others. And it also gives you an indication of any risk of adrenal crisis.

[Suffererc in reply to PMRpro]

Can GPS actually order the synacthen test . I asked for one and was told no.

[LBM1953 in reply to Suffererc]

My GP said they don't do it. Whether this is NHS policy (as Vit D tests) or just my GP - I don't know....

[Suffererc in reply to Suffererc]

To add I am currently taking 2/1.5 alternately. Pain comes back when taking a third dose at 1.5 so lose confidence to carry on. The truest would boost my confidence to drop to 1.5

[PMRpro Ambassador in reply to Suffererc]

I suspect it may be a local Trust question. The synacthen test itself is done in a day unit at a hospital but some such tests can be requested by a GP.

However - as I have explained, just asking for a basal cortisol test will give you almost as much information. All the synacthen test tells you is whether your adrenal glands are capable of producing cortisol in response to stimulation - not that they are actually reliably doing so. And a GP can do that.

[piglette]

Perhaps the Spire made a mistake, who did you talk to? Synacthen is a manufactured drug that acts like ACTH by stimulating the adrenal gland to produce more cortisol.