PRL and hyperprolactinemia: The hyperprolactinemia rest test, with serial blood sampling from an indwelling catheter as a patient rests in a quiet room, found that samples drawn at 0, 30, and 60 minutes, were sufficient to diagnose stress-induced hyperprolactinemia, with mild to moderate elevations in prolactin, between 20 and 100 ng/mL [17].