Hair loss can be caused by many things, including some medications, high fevers, hormonal changes, pregnancy, surgical shock, transplant surgery, poor diet (lacking in essential fatty acid, biotin, zinc, iron deficiency), anemia, aging, male pattern baldness, thyroid disease causing decreased thyroid levels (hypothyroidism), severe emotional stress, and autoimmune disease (disease that affects the body’s ability to recognize its own tissues, causing it to gradually destroy them).
Source: Department of Health and Human Services