Prolactin dynamics in normoprolactinemic primary empty sella: correlation with intracranial pressure

Prolactin dynamic was investigated in 43 premenopausal patients with primary empty sella (PES) diagnosed by pneumoencephalography and CT scan. Only normoprolactinemic patients were included in this study. Basal PRL levels ranged from 4 to 25 ng/ml. PRL responses to TRH (200 micrograms i.v.) and metoclopramide (MCP, 10 mg p.o.) were not significantly different from those in normal subjects, although a trend toward higher responses was present in PES patients. The administration of nomifensine (NOM, 200 mg p.o.) induced a PRL decrease, which was not significantly different from that in normal subjects. However, a sequential stimulation with TRH plus MCP (1 h after TRH administration) induced an exaggerated PRL increase which was significantly different from that in normal subjects. The peak PRL responses after stimulation were not significantly correlated with estradiol levels or FSH/LH ratios in our patients. The influence of body weight was also excluded on the basis of the responses observed in 8 obese control subjects that were significantly lower than in PES patients. Moreover, in 19 patients we studied the intracranial pressure (ICP) through an indwelling catheter inserted into the lumbar subarachnoid space. ICP was normal in 5 patients and elevated in 14 patients. When we compared PRL dynamics in patients with normal or elevated ICP, a significant difference was noted between the percentage of PRL decrease after NOM, that was lower and delayed in patients with increased ICP, suggesting an influence of ICP on neuronal dopamine reuptake. In conclusion, an augmented PRL reserve is present in premenopausal patients with PES. A correlation can be found between ICP and the function of dopaminergic neurons controlling lactotroph cells.