CSF prolactin determination in patients following operation for pituitary tumor

Serial cerebrospinal fluid (CSF) and plasma prolactin concentrations were determined from patients during prolactin stimulatory testing with thyrotropin-releasing hormone or during pneumoencephalographic stress. Six patients had been operated on for suprasellar extension of pituitary tumor and one had been irradiated for suprasellar extension of a pituitary tumor. Prior to testing, four patients had had no clinical evidence of tumor recurrence and 3 patients had had tumor recurrence. One of the recurrent tumors had again extended into a suprasellar location. Basal CSF prolactin was undetectable in all patients who had had no recurrence. In 3 of the 4 patients without recurrence, however, prolactin became detectable in CSF during stimulatory testing. CSF prolactin values also increased during stimulatory testing in the patient with suprasellar recurrence of the tumor. A basal CSF-to-plasma prolactin ratio was 0.1 or less in all patients without recurrence. In the 2 patients with recurrence but without suprasellar extension, the CSF-to-plasma prolactin ratio was 0.18 or less. The patient with suprasellar recurrence had a strikingly elevated CSF-to-plasma prolactin ratio of 1.1. Thus, an increase of CSF prolactin during stimulatory testing does not necessarily indicate suprasellar recurrence of a pituitary tumor. However, an elevated CSF-to-plasma prolactin ratio appears to remain a valid indicator of suprasellar extension despite prior pituitary surgery.