The ratio of pan‐tyrosine (pY) to serine 312 phosphorylated (pSer312) IRS1 (Y/S IRS1 ratio) was shown to decrease in response to insulin resistance in cell studies (Copps & White, 2012), and we have recently shown that it is significantly decreased in neuronal‐enriched EVs of patients with Alzheimer's disease (AD) compared to controls (Kapogiannis et al., 2015), in whom it is also associated with regional atrophy (Mullins et al., 2017). The gene discussed is IRS1; the disease is Alzheimer disease.