Endocrine Abstracts

Aim: Short Synacthen test has been widely used screening test for assessment of hypothalamo-pituitary-adrenal axis (HPA). The most widely used is 30 min plasma cortisol Post synacthen. We have compared 30 min cortisol with 60 min for assessment of the HPA axis of patients with known endocrine disorders and on long term steroid, opiate use and obesity (non endocrine disorder).

Method: Cortisol Response to 30 and 60 min post synacthen were measured in random sample of 50 patients who have undergone testing. We divided them into Endocrine, Non endocrine and miscellaneous groups. A normal response was defined as a peak concentration of ≥550 nmol/l.

Result:

i) Twenty patients were in non endocrine group. Fifteen (75%) patients out of this group failed 30 min response and four patients (25%) out of this sub group who failed 30 min had a normal 60 min response.

ii) Twenty patients were in endocrine group. Ten (50%) patients out of this group failed 30 min response and six (60%) patients out of this sub group who failed 30 min had a normal 60 min response.

iii) Ten patients did not have 60 min cortisol measured as it was clinically not indicated.

iv) All Patients who had normal 30 min response had also normal 60 min response

Conclusion: Our observations reveal that 10 out of 50(20%) patients with abnormal 30 min SST would have been categorised as false positive result indicating that 60 min SST is more reliable to avoid over diagnosing adrenal insufficiency. Interestingly in our endocrine disorder sub group who failed initially 60% had normal 60 min response which opens up the debate for need to measure 30 and 60 min cortisol or only 60 min cortisol.