Endocrine Abstracts

Macimorelin is an oral ghrelin receptor agonist that stimulates growth hormone (GH) release from the anterior pituitary. It has excellent accuracy comparable to the insulin tolerance test (ITT) or arginine and growth hormone-releasing hormone test for diagnosing adult growth hormone deficiency (AGHD). This audit evaluated safety and diagnostic outcomes of patients undergoing macimorelin testing in a tertiary endocrinology centre. A retrospective review was conducted on 17 patients evaluated between June 2023-May 2025 with 0.5mg/kg of macimorelin ingested in the morning while fasted. Median age was 52 years (range 23 to 67); four patients were female. Hypopituitarism secondary to pituitary tumour and pituitary surgery accounted for 9/17 (53%) of patients, while other aetiologies included radiotherapy (n = 2, 12%) and idiopathic hypopituitarism (n = 2, 12%). All patients reported dysgeusia, but no other adverse events occurred. Six patients (35%) maximally stimulated to 2.8 ng/mL GH threshold while 4/17 (24%) stimulated to 5.1 ng/mL. The 5.1ng/mL threshold was applied for therapeutic decision-making as previous studies comparing ITT results demonstrated higher sensitivity and similar specificity using this threshold compared to 2.8ng/mL. Eleven patients commenced GH therapy (one patient deferred as AGHDA score was low (5/25) and one disengaged). Low pre-test IGF-I had a sensitivity/specificity of 0.60/0.50 respectively with <2.8ng/mL threshold and 0.67/0.75 sensitivity/specificity with <5.1ng/mL threshold. Macimorelin testing was well tolerated, is a shorter test than alternatives and appears to be a safe and effective alternative to ITT. Pre-test IGF-I had low sensitivity and specificity in predicting AGHD diagnosed using macimorelin stimulation testing.