Thanks for posting your query.
Causes are androgenic, stress, improper diet, dandruff
You need to take diet rich in proteins and fruits and vegetables, avoid smoking
and drinking if you have that habit.
It is not easier for the lost hair to come back.
You consult a dermatologist
and if you are very specific you can also think of hair transplantation
Hope I have answered your query.
Wishing you good health.