Endocrine Abstracts

Background: Adrenocorticotrophic hormone (ACTH) measurements can help determine the cause of adrenal insufficiency (AI), but AI is diagnosed using peak cortisol levels following Synacthen stimulation, not ACTH levels. ACTH levels are high in primary and low in secondary and tertiary AI. Primary AI is rare in childhood. At Sheffield Children’s Hospital (SCH) ACTH is measured as part of screening for AI, paired with an early morning cortisol, and at baseline (0 minutes) as part of the Short Synacthen Test (SST). We performed a cost-benefit study examining potential savings from a change in practice in which ACTH is measured only in patients who fail their SST.

Methods: We conducted a retrospective analysis of all SSTs performed at SCH between 2011-2019. Our diagnostic cut-off for a pass following adrenal gland stimulation with Synacthen is a peak serum cortisol of >429nmol/l. We determined the proportion of passed and failed SSTs. We used Pearson’s correlation to determine the association between peak cortisol and ACTH. We calculated the potential cost savings of a change in practice where ACTH would be requested only in the event of a failed SST to help determine the cause of AI.

Results: We analysed 1275 SSTs, 905/1275 (71%) of which reached the diagnostic threshold for a pass. We found no correlation between baseline ACTH and peak serum cortisol (r=-0.007, P=0.836). The analysis of an ACTH sample is currently £19.14. If our practice were to change to an ACTH measurement only in the event of a failed SST a cost saving of £17,322 would have been generated over the time period 2011-2019. We calculated, based on an increase in the number of SST requests over the study time period, a current cost saving of £2,456 per annum.

Conclusions: ACTH does not correlate with peak cortisol following Synacthen stimulation. Routine ACTH measurement in the diagnostic pathway for paediatric AI is not indicated, however it is important in the differentiation of primary AI from other causes. We recommend ACTH quantification is performed only after AI is confirmed by SST and believe this change in practice would lead to cost savings.