Cortisol, 30 minutes after Synacthen
What this test measures
In the short Synacthen test an injection of a synthetic form of the pituitary hormone ACTH is given, and cortisol is measured before and 30 minutes after. The 30-minute value shows whether the adrenal glands can respond.
Why doctors request it
The standard test when adrenal underactivity is being considered, including after long courses of steroid tablets or inhalers.
What commonly pushes it up
- A healthy adrenal response
What commonly pushes it down
- Adrenal gland failure
- Suppression of the adrenals by steroid medicines as a class
- Pituitary conditions that have left the adrenals under-stimulated
Everyday reasons for a value outside the range
- The cut-off depends on the laboratory method and is lower on newer assays
- Oestrogen-containing contraception raises cortisol binding and can give a falsely reassuring value
About the sample
Usually a morning test; the baseline cortisol from the same test maps to cortisol.
Upload a photo or PDF and see every line against the range your lab printed, explained in plain English. First report free.
Read my report freeThis is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.