Higher Serum Prolactin in a Subset of Patients with Multiple Sclerosis

Background: Prolactin (PRL) has commonly been considered a potentially detrimental factor in Multiple Sclerosis (MS) and its experimental animal model, although there are also controversial results. More recently there have been reports that exclusive breast-feeding, where hyperprolactinemia is physiologically present, significantly reduces the risk of relapses occurring during postpartum. Consequently, the relation of prolactin (PRL) with Multiple Sclerosis (MS) currently remains unclear.

Objectives: To determine if serum PRL concentration is associated with clinical, neuroimaging and neurophysiological features of MS, as well as with thyroid hormonal status.

Methods: A cross-sectional observational study was conducted. Forty patients with MS and 80 apparently healthy subjects were included. All MS patients were being treated with Interferon-beta. Clinical and neuroimaging data were collected in MS patients; visual, auditory and somatosensory evoked potentials were registered. In all patients and control subjects serum concentration of PRL, TSH, T3 and T4 were determined.

Results: The female:male ratio for MS patients was 5.6:1, with a mean age of 41.3 ± 12.5 years. Relapsing remitting (RR) MS predominated (85 %). A significant increase of PRL was observed in MS patients with respect to controls; this difference was present in female patients, but not in men with MS. In a subgroup of MS patients (n=7, 17.5%) PRL concentration was above 450 mUI/L, while in control subjects PRL levels ranged from 106 – 426 mUI/L. All patients with elevated PRL levels had RR-MS, nevertheless no statistically significant difference was encountered between the different clinical forms.  PRL concentration was not associated with main neurological symptoms at onset and currently, degree of disability (EDSS), years of disease, annual relapse rate, the overall number of MRI lesions or their localization, nor with the presence of abnormal evoked potentials. PRL concentration displayed a significant correlation with TSH levels (r=0.425, p<0.05), but not with T3 and T4.

Conclusions:

Higher serum PRL concentrations in a subset of MS patients were not associated with clinical, neuroimaging and neurophysiological features, but could be linked to thyroid hormonal status.