Actually I think it is the test boosters that do it.
I don't notice any head-hair change at all. Forme, it is only facial hair that stops growing.
I would suggest the test boosters for at least a few weeks. I would also suggest that you stay off for a couple months.
For me, the indication that I have been off long enough and normal test production is good is that I start getting acne on my chest. I am 43, so I don't normally get acne any longer. So when I do, I know my test production is good. I think that riding on your own test for a couple months would help a lot with your hair.