Decreased neurofilament light chain levels in estriol‐treated multiple sclerosis

Estrogens have neuroprotective actions depending on estrogen type, dose, and timing in both preclinical models and in women during health and disease. Serum neurofilament light chain is a putative biomarker of neurodegeneration in multiple sclerosis, aging, and other neurodegenerative diseases. Here, oral treatment with an estrogen unique to pregnancy (estriol) using an 8 mg dose to induce a mid‐pregnancy blood estriol level reduced serum neurofilament light chain in nonpregnant MS women at mean age of 37 years. This is consistent with estriol‐mediated protection from neuro‐axonal injury and supports the use of serum neurofilament light chain as a biomarker in MS.