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Endocrine Abstracts (2023) 90 P154 | DOI: 10.1530/endoabs.90.P154

ECE2023 Poster Presentations Pituitary and Neuroendocrinology (123 abstracts)

Clinical utility of the Octreotide Challenge Test in Acromegaly

Irfan Khan , Muna Guma , Yaasir Mamoojee & Andy James


Royal Victoria Infirmary, Endocrinology and Diabates, Newcastle upon Tyne, United Kingdom


Background: Acromegaly is a rare condition characterised primarily by tumourous production of excess Growth Hormone (GH) from a pituitary adenoma. The Octreotide Challenge Test (OCT) has been used in the RVI to predict short term efficacy of long-acting Somatostatin Analogue (SSA) therapy.

Aims: We retrospectively reviewed the OCT results of all patients with acromegaly treated at RVI from 2005 to 2021 to evaluate its clinical utility.

Methods: OCT protocol: blood sampling for GH is undertaken at baseline and then hourly for 6 h after SC administration of 100 mg of short-acting Octreotide. Data extracted: patient demographics, baseline GH and nadir GH on OCT, IGF1 level at presentation and after long-acting SSA therapy, follow-up MRI findings after SSA therapy.

Results: 46/79 patients diagnosed with acromegaly had OCT. Female to male ratio was 3:2, with a mean age of 49 years and mean IGF1 of 3xULN at diagnosis. All patients demonstrated a reduction in GH on OCT, with a mean reduction of 72%. 25 patients received SSA pre-surgery or as long-term medical therapy. There was no relationship between reduction of GH on OCT and IGF1 suppression on SSA. Females were more likely to experience >50% reduction in IGF1 on SSA compared to males (78% vs. 56%, P=0.04). 18 patients underwent repeat imaging >6 months after SSA initiation and/or before surgery. Tumour shrinkage were demonstrated in 67% of cases. Shrinkage was most likely to be observed in females (66% vs. 33%, P<0.05). Average GH reduction on OCT was 68% in patients who demonstrated tumour shrinkage compared to 83% in those who did not (P<0.05).

Conclusions: OCT does not predict biochemical response to SSA therapy in our cohort. Female patients are more likely to have a better reduction in IGF1 and tumour shrinkage on SSA therapy compared to males. Tumour shrinkage is inversely related to GH reduction on OCT in our cohort.

Volume 90

25th European Congress of Endocrinology

Istanbul, Turkey
13 May 2023 - 16 May 2023

European Society of Endocrinology 

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