Elevated insulin‐like growth factor‐1 in patients without clinical evidence of acromegaly

Abstract

AbstractObjectivesTo (1) identify the frequency of IGF‐1 elevation in a cohort of patients without clinically suspected GH excess, in a state‐based reference laboratory over a 24‐month period, and (2) to examine potential differences in comorbidities and relevant medications between people with an elevated IGF‐1 compared to a matched control group.DesignAll IGF‐1 measurements at Pathology Queensland between 1/12/2018–1/12/2020 were identified. The medical records of those with IGF‐1 ≥1.1x the upper limit of the reference range were appraised to determine: (1) documentation of acromegalic features, (2) relevant comorbidities and medication use, and (3) further investigations to exclude pathological GH excess.Patients and MeasurementsThere were 2759 IGF‐1 samples measured in 1963 people ≥18 years, over the specified period. Of these, 204 had IGF‐1 ≥1.1x the upper limit of the age‐matched reference range; 102 cases (61M, 41F) met inclusion criteria, and were matched to 102 controls with a normal IGF‐1 based on age, sex, gonadal status and pituitary anatomy on MRI.ResultsThere were significant differences in the frequency of dopamine agonist use (19/102 cases vs. 6/102 controls, OR = 3.66, 95% confidence interval [CI]: 1.45–9.29, p = .009) and chronic kidney disease (CKD) (14/102 cases vs. 4/102 controls, OR = 3.90, 95% CI: 1.28–11.14, p = .024).ConclusionsOut of 1963 patients having IGF‐1 measured, 102 (5.2%) had an elevated IGF‐1 where there was no known acromegaly, GH replacement or endogenous glucocorticoid excess. Intraindividual biological variability, assay imprecision and physiological factors are known contributors to falsely elevated IGF‐1, dopamine agonist therapy and CKD should also be considered.