Prolactin stimulation in multiple sclerosis--an indicator of disease subtypes and activity?

Prolactin (PRL) belongs to the growth and lactogenic hormone family and has potent immunomodulating properties. Mild hyperprolactinemia has been found to enhance several autoimmune diseases and increased PRL plasma levels have been described in the experimental multiple sclerosis (MS) model while the PRL antagonist bromocriptine was able to suppress the disease. As studies of PRL serum levels in MS have led to conflicting results we investigated further the question of prolactin alterations in MS. We correlated PRL baseline values in a large sample of 132 MS patients with disease course and activity. Furthermore, inhibitory (bromocriptine) and stimulatory (metoclopramide) tests were performed in a subsample (n = 39) to gain functional information. We found no correlation of baseline values with disease course or activity. Nevertheless in the regression analysis of stimulatory test results, 14% of the variance was attributable to disease activity. In conclusion PRL does not seem to be relevant as an activity marker in the whole MS population.