Diurnal prolactin changes in human cerebrospinal fluid.

Eight adult male patients suffering from hydrocephalus of differing aetiologies were investigated in order to detect the existence of diurnal variations of prolactin (PRL) concentration in human cerebrospinal fluid (CSF). Blood and ventricular CSF samples were taken every 2 h during the day (0800-2200 h) and every hour during the night (2300-0700 h). CSF mean PRL levels showed significant nyctohemeral variations with low levels (2.1 +/- 0.3 ng/ml) during day-time and higher levels at night (3.3 +/- 0.1 ng/ml), similar to that observed in serum (PRL values: 16.4 +/- 5.2 and 24.8 +/- 4.3 ng/ml during day and night periods respectively). The presence of a 24 h CSF PRL secretory profile similar to that in serum was shown in six patients with normal 24 h mean PRL values and normal diurnal changes in serum. In two patients with an altered serum 24 h secretory pattern no significant nyctohemeral variations in CSF PRL levels were found. Present data show the existence in man of nyctohemeral variations in CSF PRL content related to the 24 h changes of PRL levels in serum.