3 minute lightning oral presentation (and poster) ESA-SRB-APEG-NZSE 2022

Evaluation of elevated IGF-1 in patients without clinical evidence of acromegaly (#128)

Laura Careless 1 , Warrick Inder 1 2 , Carel Pretorius 3 , Lisa Hayes 1
  1. Department of Diabetes and Endocrinology, Princess Alexandra Hospital, Brisbane, Queensland, Australia
  2. Academy for Medical Education, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
  3. Pathology Queensland, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia

Aims: IGF-1 acts downstream of GH mediating many of its effects. It is the recommended screening test for acromegaly, in evaluating pituitary incidentalomas and possible hypopituitarism. Case-based observations suggest elevated IGF-1 may occur in patients without acromegaly. The aims were to 1) identify the frequency of elevated IGF-1 without evidence of GH excess, and 2) to examine potential differences in relevant medications and comorbidities between people with an elevated IGF-1 compared to a control group matched for age, sex, gonadal and pituitary status.

Methods: All people whose IGF-1 was measured at a single reference laboratory between Dec 1st 2018 – Dec 1st 2020 were identified. Electronic records of those with at least one IGF1 >1.1x the upper limit of the age-matched reference range were appraised to determine; 1) documentation of acromegalic features, 2) presence of relevant comorbidities and medication use, and 3) further investigation to exclude pathological GH excess. There were 2759 IGF-1 samples measured in 1963 people ≥18 years, over the specified period. Out of these, 204 had IGF-1 >1.1 times 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. 

Results: There were significant differences in the frequency of dopamine agonist use (19/102 cases vs 6/102 controls, OR=3.66, 95%CI: 1.45-9.29, P=0.009) and chronic kidney disease (CKD) (14/102 cases vs 4/102 controls, OR=3.90, 95%CI: 1.28-11.14, P=0.024).

Conclusion: Out of 1963 patients having IGF-1 measured, 102 (5.2%) had an elevated IGF-1 where there was no known acromegaly, GH replacement or glucocorticoid excess. There were significant associations with dopamine agonist use and CKD. While assay imprecision, intra-individual biological variability and accuracy of reference ranges probably represent the main influences on the prevalence of elevated IGF-1, we have identified two additional factors which should be considered.