Endocrine Abstracts

Background: Accurate assessment of GH & IGF1 status in acromegaly is crucial for informing management to minimise excess morbidity/mortality. Expert panels have differed with respect to recommended testing modalities and thresholds – the most recent being the Endocrine Society 2014 guidelines. We evaluated their simplified algorithm, which minimises the need for day-case testing, against other more resource-intensive measures.

Methods: A retrospective analysis was performed of prospectively collected data from a cohort of 51 patients with acromegaly, who received up to 6 months of pre-surgical medical therapy prior to transsphenoidal surgery. Single 0900 h GH and IGF1 levels were recorded at diagnosis, post-medical therapy and post-surgery. OGTT nadir was determined at diagnosis and post-operatively. GH day curve mean (GHDC) was measured at diagnosis and after medical treatment.

Results: A single 0900 h GH value correlated well with GHDC results both at diagnosis (R²=0.94, P<0.0001) and following medical treatment (R²=0.92, P<0.0001). Three patients were below the suggested target of 1 μg/l on a single GH reading post-medical therapy, but had a GHDC >1 μg/l; all three had an IGF1 above the upper limit of normal (ULN). Four patients had a 0900 h GH >1 μg/l, but a GHDC <1 μg/l and an IGF <ULN. Post-operatively, a single 0900 h GH reading of <1*** μg/L was observed in 3 patients who failed to suppress to <0.4 μg/l on an OGTT, although suppression in each case was to <1 μg/l; two of these had an IGF1 >ULN. Five patients with a 0900 h GH >1 μg/l suppressed to <0.4 μg/l on OGTT; IGF1 was <ULN in one of these.

Conclusions: In the majority of patients, a single measurement of GH status together with IGF1 provides an accurate assessment of biochemical control in acromegaly. For the small number of cases in whom 090 h GH and IGF1 are discordant, GHDC (post-medical therapy) and OGTT nadir (post-surgery) remain important adjuncts.