@Zeno I don't have much personal experience with pregnenolone but I have dealt with male pattern hair loss for years with varying degrees of success. I've also used anabolic steroids off and on over the last decade so I have personal experience with changing hormone levels.

There's a lot of pet theories on hair loss, but personally, I think many see and experience hair loss due to rapid changes in their hormone levels, possibly changes to certain ratios of hormone levels, rather than the absolute levels of hormones, i.e., it's the delta and the ratios that matter, not the total concentrations. This is just based on personal experiences taking a number of hormones and hormone modulating substances over many years.

After stopping for awhile, if you found benefit from pregnenolone and want to try it again, you might try tapering up over a long period of time from lower doses. 10 mg/d for 2-3 weeks. Then 20 mg/d for 2-3 weeks. Then 30 mg/d for 2-3 weeks, etc.

Just a matter of finding the right intensity and exposure. You probably don't want to be basking under a mercury vapor light for extended periods any more than you want to be spending all day without clothes in direct south Texas sun. With UV, some is good, overdoing it likely not. But you could hypothetically spend all day under infrared lamps and it would only be beneficial.

UV-B and UV-C are the more dangerous types of UV light--they are lower wavelength, higher energy/intensity. UV is non-ionizing, but still very high energy photons that can cause a lot of photochemical reactions.