Blood-cerebrospinal fluid barrier for prolactin in empty sella syndrome

In six patients with "empty sella" syndrome (ESS), three primary (pESS) and three secndary (sESS), the ratio of serum to cerebrospinal fluid (CSF) concentrations of prolactin (PRL) was 6.6 +/- 0.7 (mean +/- SEM) (range 5.5--9.6), with a significant correlation between serum and CSF levels of PRL (r = 0.93 p less than 0.01). A control group of ten normal subjects showed similar values. The hyperprolactinemia found in two cases of pESS did not change the serum/ CSF ratio of PRL. The acute release of PRL into the serum following TRH i.v. did not increase the PRL level in CSF either in control subjects or ESS, with one exception. In a case of sESS consecutive to the treatment with bromocriptine (for 6 months) of an invasive prolactinoma, TRH i. v. released PRL into the CSF but not into the blood, and the serum/ CSF ratio of PRL was very low, until a new cure with bromocriptine (for 3 months) mormalised it. It is suggested that the blood-CSF barrier for PRL is similar in ESS and in normal subjects, with the exception of sESS following incomplete remission of some invasive prolactinomas, in which the high permeability of BCB may be explained both by hemodynamic changes in the pituitary portal vascular system and by a new source of PRL which release it directly into the CSF, bypassing the blood route.