Northwest Community Healthcare Browse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 Brittle nailsBackBrittle nailsLike the skin, the fingernails are a reflection of a person's state of health. Low levels of zinc and iron as well as thyroid problems can cause brittle nails. However, brittle nails are often a normal result of aging. A.D.A.M. content is best viewed in IE9 or above, Firefox and Google Chrome browser.Content is best viewed in IE9 or above, Firefox and Google Chrome browser.