How to Naturally Thicken Hair - Clinically Proven Methods 

This is probably the most powerful list on thickening hair https://humancure.com/10-ways-to-thick-hair/ . Will work faster on women than men, as men's hair loss is harder to tackle (but not impossible to at least halt and grow back at least some hair).
Hair growth is complicated, hence the reason you tackle it from various angels - including nutrition, hormones and more as explained - if you only do 1 thing from it, you may not get any results, you need to do at least 3 or 4 things to get the best results. Please see article for more details on building a regime to thicken hair naturally.