Female hair loss, thyrod test came out fine. What causes it?

FPHL. Fphl has a strong genetic predisposition although the mode of inheritance remains to be determined. There are many genes that contribute to this condition, and these genes could be inherited from either parent, or both. Genetic testing to assess risk of balding is currently not recommended, as it is unreliable. Currently, it is not clear if androgens (male sex hormones) play a role in fphl.