Hair loss is a systemic problem. Topical estrogen won't fix the underlying metabolic issue. But until the metabolism is fixed, maybe topical caffeine, progesterone, aspirin, low dose DHEA would be safer than E. There's so much E in the environment that it's hard to avoid it even if you try, & everything applied topically definitely gets systemically absorbed.
Also nicotine gum, bromocriptine, pro-dopamine/anti-5ht substances reliably thicken my hair. I think nicotine is safer than E.
How much nicotine do you take? Even 2mg chewed a little bit seems very strong to me.