Topical Thyroid Hormones for Hair Regrowth

There are two drugs of interest in the thyroid hormone family: triiodothyronine (T3) and thyroxine (T4). Past research has already shown that both can either prolong the anagen phase of the hair follicle cycle or mitigate hair stem cell apoptosis (desirable traits of hair loss treatments). The synthetic versions of T3 and T4, l-triiodothyronine and l-thyroxine, have well-documented pharmacokinetics, as they are both frequently prescribed orally today for hypothyroidism. While T4 is converted intracutaneously into T3 by the deiodinase enzyme, T4’s additional downstream pathways may also play a role in its hair growth effects. The study would be conducted on human scalp skin in organ culture, building off Paus et. al’s 2008 study on human hair follicles in organ culture. The primary differences between the previous ‘08 study and the current study are the organ tested and the application method: the ‘08 study was tested on hair follicles extracted from the scalp through a solution infused into the culture itself, whereas our study will be tested on scalp skin through a topical solution. In the ‘08 study, T4 increased hair matrix keratinocyte proliferation and prolonged the anagen phase of the hair follicle cycle, while T3 mitigated hair matrix keratinocyte apoptosis.