The utility of serial prolactin sampling in healthy adult volunteers

Background: Stress hyperprolactinemia is a common cause of elevated prolactin (PRL) and often leads to additional investigation and radiation exposure. The results of PRL serial sampling in healthy adult volunteers to determine the utility of delayed collection are reported. Methods: Cannulated serial PRL samples were collected from 30 healthy adult volunteers between April and May 2018 at 20-minute intervals from arrival to 60 minutes (T0, T20, T40 and T60). Exclusion criteria were known risk factors for hyperprolactinemia, and patients fasted for six hours. Cortisol (CORT) was collected as a surrogate marker for stress. Results: Thirty (30) adult volunteers (n = 15 female) had a mean age of 34.7 (+/- 9.5), and mean baseline PRL of 9.7 μg/l in males and 15.8 μg/l females. Elevated PRL-T0 was observed in four volunteers (n = 3 male), all of which normalised at different intervals by T60 with serial sampling. The highest PRL was 33.7 μg/ml, normalised at T20, and had concomitant elevated cortisol levels, which remained elevated at T60. The delta decrease (Δ) for PRL was negative for all intervals (p < 0.05) and mirrored the delta decrease of cortisol (p < 0.05). Conclusion: In 30 healthy adult volunteers presenting for cannulated serial PRL sampling, four had elevated baseline levels that normalised at different intervals up to T60. The delta decrease (Δ) for PRL was negative for all intervals.