My Granddad grew his hair at 82

My granddad, with the cleanest bald head ever, was prescribed Dutasteride 2 years back for some prostate issues and has grown a full head of hair since then, with follicles never seen before sprouting up. I’d never seen him with a single strand of hair my entire life. He got more hair than his 21-year-old grandkid now lol (and pretty dense too)

I have seen the same results from finasteride (Proscar 5mg dose) in elderly men (not extreme reversal as you reported, but a respectable regrowth of hair in a 75 y/o male). It gives us hope that the stem cells for advanced balding are still alive and can be stimulated.  We are now seeing men in their 40s and even their 50s using microneedling and getting growth from an area with no hair for more than two 2 decades.  The problem with microneedling is that we don’t have experience on how long the new hair induced by this process will last.  I tell those who try and get results to set up a maintenance schedule, possibly by reducing the microneedling from once a week to once a month.