How can testosterone cause both hair growth and loss, and are there other effects that switch?

How can testosterone (‘T’) cause both hair growth and hair loss? Type “testosterone hair” in Google and the top two suggestions are:
testosterone hair loss
testosterone hair growth
I’ve read some stuff but I still don’t get it. Nothing seems to mention the relationship between the two. T is a hormone that causes body hair growth at puberty; at what point or factors does T invert and do the opposite of what it originally is for?

I’ve had lifetime low T, and when I take T treatments (e.g. by an endocrinologist’s prescription, or on a supplement like creatine which as a side-effect raises T availability), I notice the effects that T is supposed to have. It’s a little bit like I’m going through a form of puberty again because I never fully got the hormones to begin with. Like I think my singing voice is lowering a little bit, and I think I notice a tiny bit more hair growth.

Hair growth/loss in and of itself is a minor issue, but my bigger question is: Are there other T effects that will REVERSE themselves at some point? T affects bone density and muscle mass, THOSE are important. Will T always increase those a man’s whole life, or do those reverse or lessen too??

Thanks for the help as always, guys!

It is not really reversal or switch of effects … it is different effects in different locations and at different ages. What happens to pubic hair is not the same as what happens to scalp hair, for example … and both are different than those annoying long ear hairs.

The “how” is because what happens as T (or one of its more potent products, like dihydrotestosterone, DHT) hits receptors and what happens as it hits receptors varies by location and age, and changes in local conversion of T to DHT with age that varies by location.

No idea if there are other changes of the impact of the same level of T that occur with age.