Rooney JPK, et al. – The role of hormonal risk factors for amyotrophic lateral sclerosis (ALS) was examined among women from 3 European countries in this large case–control study. The clinicians found an association between exogenous estrogens and progestogens and reduced odds of ALS in women. Across the countries included, these outcomes were at variance with previous findings, which could be partly explained by differential regulatory, social, and cultural attitudes toward pregnancy, birth control, and HRT. The results demonstrated that hormonal factors could be important etiologic factors in ALS. However, a full understanding required further investigation.