A great article from The American Academy of Dermatology Association, who explain the possible reasons Men and Women experience hair loss.
These range from Male/Female patterns baldness, Alopecia, PCOS, Post Partum, medication and many more.
Losing hair is a very common occurrence, some people take it in their stride and accept their fate, however for many more its an incredibly stressful and self conscious time.
There are plenty of options that can be taken to help slow down the speed at which someone loses their hair, as well as hair toppers/wigs, hair transplants & Scalp Micropigmentation.
Whatever option you decide is right for you, just make sure you have really done your research into the company and specialist that will be working with you.