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Synacthen test

My son is having a Synacthen test tomorrow in the afternoon - I know what it is for but don't know what it entails. Any advice greatly appreciated. Also everything I have read says it should be done in the morning but his is at 2pm am a little confused by this. He has also just increased his Pred from 20mg to 40mg and was wondering if this would affect the result.

Thanks in advance,

4 Replies


i am not sure if this is any help but i recently had the same test.

i had it at 3pm so i am not sure that the time has any hugh effect (i am not 100% sure about that)

also they only wanted to do it when i was of pred, i am not sure why but i think it will possibly have an effect on the results especially of you have just increased.

it might be worth contacting them before hand to check.

i hope that helps but i am sure somone with much more knowledge will be along with a better answer in a bit.




Pred will affect the result they usually like u to not take it or any other synthetic steroids before the test.

They wil take a blood sample to establish a base line costisol level. They wil then give ur son some acth which in normal situations stimulates the adrenal glands to produce costisol. After 60 mins they wil then take another blood sample and see wot the costisol level is.

In hypoadrenalism the body doesnt produce costisol and acth doesnt provoke a response from the adrenal glands.

If this is the case then ur son will need to take steroid replacements usually in the form of hydrocortisone!

The prob wit pred is it will falsly increase the base line costisol level. It is fine usually howeva to take the days dose after the test. Ur other question was about time of day. In true adrenal suppression it doesnt matter wot time of day the test is done as the level of costisol will b low all the time. When they measure costisol levels they are usually higher first thing in the mornin around 9am and then gradually lower thro the day reachin their lowest as u go to bed.

Get in touch wit the dr who has organised the test and ask him/her about the pred my unmedical opinion of this is that u shud prob take it after the test is complete but double check wit the medics to b sure.

Feel free to pm me if i can help anymore. And hope the test goes ok. Its fine and is only as painful as any blood sample so hopefully ur son shud not find it too bad. It may make him feel a little nauseous it did wit me. The main thing is 4 him to try n stay calm and stil durin the 60mins waitin period. Hope all goes well tho hon. Take care lv kitkat Xx


I had to be converted to dexamethasone a week before to have synathen test as was told they couldn't do it if on pred due to the way the drug releases over time affecting the result. My endocrinologist said was pointless to do a short synacthen if on pred.


Thanks for the replies. The test was postponed as Jay has just increased his Pred due to an allergic reaction on Wednesday (Bad timing there!) It has been re-booked for 2 weeks time so we can get back to the maintenance dose of 10mg, apparently this is ok and the result can be worked out from this.


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