Elevated Prolactin Levels Are Associated With Increased Severity and Psychiatric Symptoms in Anti-N-Methyl-D-Aspartate Receptor Encephalitis

Autoimmune encephalitis, predominantly anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis, is a central nervous system (CNS) autoimmune disorder. Prolactin (PRL), a pro-inflammatory hormone implicated in autoimmune pathogenesis, may play a role in anti-NMDAR encephalitis, though its clinical relevance remains unclear.

Serum PRL levels were compared between anti-NMDAR encephalitis patients and healthy controls (HCs). Correlations between PRL levels and disease severity were analyzed. Subgroup analyses were performed based on clinical manifestations, tumor comorbidity, ICU admission, disease severity, and MRI abnormalities. Longitudinal PRL levels and modified Rankin Scale (mRS) scores were evaluated in 28 patients during follow-up. In addition, associations between PRL and inflammatory markers, including neutrophil-to-lymphocyte ratio (NLR), were investigated.

Anti-NMDAR encephalitis patients exhibited significantly elevated PRL levels compared to HCs (p < 0.001), with PRL positively correlated with baseline disease severity. After a 3-month treatment period, both PRL levels and mRS scores decreased significantly (p = 0.002, p < 0.001, respectively), and their reductions showed a positive correlation (r = 0.407, p = 0.032). PRL levels were associated with psychiatric symptoms but not with seizures, prodromal fever, speech deficits, or sleep disturbances. Furthermore, PRL abundance correlated with systemic inflammatory markers, notably NLR.

Circulating PRL levels are significantly elevated in anti-NMDAR encephalitis and correlate with disease activity, suggesting its potential utility as a biomarker for monitoring disease progression. The pathophysiological role of PRL-whether pathogenic or protective-warrants further investigation.