There are many reasons why someone may be losing their hair, including vitamin deficiency, hypothyroidism and stress, Amanda Gardner of Health.com reports. It is also possible that too much vitamin A can cause a person to lose hair.
Ms. Gardner reports that some women lose their hair when they are pregnant, while others lose their hair because they do not get enough protein, which causes the body to shut down hair growth. Men tend to lose their hair due to a combination of genetics and men's hormones, called male pattern baldness. Females can also lose their hair due to genes they inherit.