Is Tretinoin topical used for hair loss?

Tretinoin may help some types of hair loss but not most. Tretinoin added to minoxidil can increase the potency of minoxidil for males using minoxidil for androgenetic alopecia. I have included reference to a well known study below. Tretinoin can cause irritation and rarely trigger a telogen effluvium when applied topically.  Prescriptions are needed and this should only be used if under care of a specialist. It is important for you to be aware this is not a common treatment and for you to be aware it has a low likelihood of helping.Reference Efficacy of 5% minoxidil versus combined 5% minoxidil and 0.01% tretinoin for male pattern hair loss: a randomized, double-blind, comparative clinical trial.
Randomized controlled trial. Shin HS, et al. Am J Clin Dermatol. 2007.

“Formula 82M” is a customized compounded prescription solution that contains the FDA-approved hair growth medication Minoxidil plus Tretinoin, Retinoic Acid for enhanced penetration and a sophisticated blend of anti-inflammatory, antioxidant, anti-androgen and other ingredients in a non-irritating propylene glycol-free base. It is only available from compounding pharmacies and does require a doctor's prescription.

Tretinoin is medication used for the treatment of acne and acute promyelocytic leukemia. I will do nothing to address hair loss