Pathological hyperprolactinaemia may be associated with hypogonadotropic hypogonadism. There are many physiological causes of hyperprolactinaemia such as pregnancy and stress. A single elevated non-rested prolactin level may lead to overdiagnosis and unnecessary pituitary imaging [1]. We conducted a study to demonstrate that a time-based rested prolactin testing reduces the overdiagnosis of hyperprolactinaemia.
Study patients were recruited from January 2019 to July 2023 through Royal Prince Alfred Hospital (RPAH) Endocrinology if there was a single elevated serum prolactin level. Patients were referred from RPAH Fertility Unit and Endocrinologists. Exclusion criteria included symptomatic or medication-induced hyperprolactinaemia, history of pituitary disorder and macroprolactinaemia.
Thirty-two patients were included (29 females, 3 males). Mean age was 33.7 (±8.5 SD) years. Fifty-three percent of the cohort were Caucasian. The pre-testing prolactin mean was 975mIU/L (±531 SD). Nine out of 32 patients had a normal rested prolactin (≤500mIU/L) at baseline. At completion, 18 patients had a prolactin level >500mIU/L. Sub-analysis indicated four more patients would have likely achieved a prolactin level ≤500mIU/L if rested longer.
[1] Whyte MB, et al. Importance of cannulated prolactin test in the definition of hyperprolactinaemia. Pituitary 2015:18(3);319-25.