Hyperprolactinemia in multiple sclerosis.

In order to clarify endocrine abnormalities due to hypothalamic involvement in multiple sclerosis (MS), serum prolactin levels were measured in 27 patients with MS and 22 healthy subjects. The presence of hypothalamic lesions was also studied by magnetic resonance imaging (MRI). Serum prolactin levels were found to be significantly higher in MS patients than in healthy controls in both sexes. Although only one patient had galactorrhea, one-third of the MS patients had mild to moderate hyperprolactinemia, which was a 4-13-fold increase over the mean value of healthy subjects. The results of thyrotropin-releasing hormone, sulpiride, L-DOPA and bromocriptine loading tests suggested a hypothalamic dysfunction, rather than pituitary prolactinoma in MS patients. Four of eight patients with hyperprolactinema had diencephalic hypothalamic lesion(s) contiguous with the third ventricle on the brain MRI, while none of the normoprolactinemic patients had any lesions in the diencephalon. All relapsing-remitting patients with hyperprolactinemia showed a rise in prolactin levels in the acute stage of the relapse and a decrease during the recovering stage and the following remission phase. Our findings suggest that latent hyperprolactinemia due to hypothalamic dysfunction occurs frequently in MS patients in relapse. The increase of serum prolactin is considered to be a sensitive indicator for hypothalamic lesions in MS.