Yeah, great words wemustchange.
The thing is DHT is not the only issue here. In theory finasteride inhibits 5ar from reducing testosterone and DHEA into more powerful forms of androgens. But thats only half of the equation. Simplifying: [androgen] + [androgen receptor] <-> [gene expression].
Reducing androgens will reduce the extension of the reaction. However, there are several mechanisms within our cells that can mediate gene expression throught co activators and other facilitators that ultimately end up increasing the mRNA transcriptional factors resulting in "one androgen" producing more target proteins by the rybosome than what it should be producing. Thats what people usually call as "sensivity".
So yeah, if you think getting on finasteride is going to save your hair, forget it. It might only get you some years tops. The best thing you can do here is a combination of treatments such as 5ar inhibitor + topical androgen antagonist + (maybe) systemic antiandrogen IF you feel like taking the chance (notice there are weak treatments such as spironolactone or stronger such as cypro). This is as far as you can get to prevent hair loss. To stimulate regrowth, which is fairly a different story, your best option is minoxidil and maybe topical estradiol.