Resting Prolactin Measurements: a useful step in hyperprolactinaemia assessment

Abstract

Abstract Objective Elevated prolactin levels are a common reason for referral to Endocrinologists but are frequently normal on repeated testing. We audited results of resting prolactin measurements to investigate whether routine testing in assessment of mild hyperprolactinaemia might improve the referral pathway. Results We identified all patients with resting prolactin measurements at ADHB Endocrinology (Auckland, New Zealand) between 2019–2020 and extracted relevant information from clinical records. 71 patients were identified: their average age was 33 (11) years; 58 (82%) were female; and the mean prior prolactin was 676 (257) mIU/L [range 245–1516, 12 (17%) > 1000 mIU/L]. 47/71 (66%) patients had a resting prolactin in the normal range. 29/52 (56%) of resting tests were normal at baseline, with the majority normal by 30 minutes. Only 1/11 tests decreased from elevated to normal between 30 and 60 minutes. Neither the level of previous prolactin measurements (> or < 1000 mIU/L), whether the indication for prolactin measurement was appropriate or not, or the highest pre-endocrinology assessment prolactin accurately predicted a normal resting prolactin. In summary, measurement of resting prolactin prior to an endocrinology clinical review is likely to identify individuals with normal prolactin who do not require a clinical assessment.