Hereditary thinning or baldness (also called androgenetic alopecia): This is the most common cause of hair loss. It affects men and women. About 80 million people in the United States have hereditary thinning or baldness.
When men have hereditary hair loss, they often get a receding hairline. Many men see bald patches, especially on the top of the head. Women, on the other hand, tend to keep their hairline. They see noticeably thinning hair. The first sign of hair loss for many women is a widening part. In rare cases, men see noticeably thinning hair. And in rare cases, women can see a receding hairline or bald patches. The reasons for this are unknown