To access growth hormone (GH) replacement on the Australian Pharmaceutical Benefits Scheme, adults with acquired pituitary insufficiency must undergo stimulation testing to confirm GH deficiency (GHD), however US Endocrine Society Guidelines recommend that the presence of deficiencies in three or more pituitary axes strongly suggests the presence of GHD, and in this context provocative testing is optional [1,2]. The commonly performed glucagon stimulation test (GST) takes up to five hours and requires admission to an ambulatory treatment ward. We aimed to identify clinical and biochemical predictors of GHD that could be used to simplify or shorten GST duration [3].
A prospective observational study of GST performed at Royal Melbourne Hospital from January 2019 to June 2023 was conducted and approved by local ethics committee.
Of the 94 GST performed, , n=74 (79%) were consistent with GHD . Abnormal GST was associated with deficiency of ≥2 pituitary hormone axes (p<0.0005), resected macroadenomas >1cm (p<0.05) and prior cranial irradiation (p =0.02). All 27 individuals with undetectable baseline fasting GH had GHD, while six patients had fasting GH above the stimulation threshold of 3.0mg/l, thereby had normal GH axis and did not require GST. Receiver operator curve analysis of the ability of fasting GH to predict GHD returned an area under the curve of 0.902 (95% CI 0.8230 – 0.9818, p<0.0001). The combination of ≥ 2 pituitary hormone deficiencies and fasting GH <0.5ug/L had a positive predictive value of 98% for diagnosis of GHD.
Measurement of fasting GH has potential to identify individuals with GH sufficiency, thereby obviating the need for prolonged, costly stimulation testing. The combination of fasting GH and pituitary hormone deficiencies predicted GHD in our centre, work has commenced to verify this finding in an independent cohort as well as in the paediatric setting