IGF-1 is a hormone that is used for diagnosing and monitoring acromegaly. There has been discussion regarding the appropriateness of current reference intervals and positive flagging rates of IGF-1 concentrations over the past few years - this included an Australia-wide IGF-1 survey. A recent paper suggested that in up to 5.2% of cases IGF-1 levels were elevated without a clinical diagnosis of acromegaly. 1 We reviewed IGF-1 concentrations and associated age and gender associated reference intervals as measured on the Diasorin Liaison at a large referral laboratory over the last five years. Over 100,000 results were available for review. Our data indicates that there has been an earlier peak of IGF-1 concentrations for both men and women, which may have led to increased flagging rates over time. Patient based quality control over the study period also suggested that these observations are based on physiological factors rather than analytical performance of the assay.