Ah, but why the hormonal change? That is the question. Constipation of the body causes the body to compensate in many ways to save your life.
In my view hair growth increases with age because the body is able to use this as an elimination pathway for excess accumulation. But then those that eventually lose their ability to grow hair have reached a 911 constipation level that has clogged even this pathyway.
This is not a good situation because accumulations will now build elsewhere in the body (tumors, cysts, polyps, etc).