Endocrine Abstracts

Aim: To asses the significance of single 60 min serum cortisol level compared to conventional approach in short synacthen test (SST).

Methods: Retrospective analysis of cortisol values in SST. Serum cortisol values at baseline, 30 min and 60 min were recorded. Rise of serum cortisol level to >550 nmol/l and a rise of >200 nmol/l from baseline is considered to be a negative test for hypoadrenalism.

Results: About 168 patients were studied, 52 (31%) were males and 116 (69%) were females. The mean age was 49+17.1. The mean basal cortisol values include, basal: 407+190 nmol/l, 30 min: 697+199 nmol/l and 60 min: 797+216 nmol/l. The mean rise in cortisol between 30 and 60 min was 101+63.6 nmol/l.

Eleven patients (6.5%) had hypoadrenalism or true positive results.

Out of the remaining 157 patients, 135 had negative tests both at 30 and 60 min. Six of them (3.6%) did not fulfil our criteria but had very high baseline cortisol levels and therefore considered as false positive results both at 30 and 60 min. Thirty-three patients (19.6%) had false positive results only at 30 min This may either be due to failure to fulfil our cut off values or it may just be an apparent failure with premature stimulation.

Patients diagnosed with hypoadrenalism had true positive results both at 30 and 60 min. Therefore no patient would have been missed in this study group, had testing at 30 min been omitted.

Conclusion: In our cohort, 30 min cortisol testing in SST, produced a number of false positive results which is reduced significantly if testing is only done at 60 min.

Single sixty minutes cortisol value during SST is cost effective, reliable in excluding and equally effective in detecting hypoadrenalism.