Pilot evidence that topically applied triiodothyronine can stimulate hair growth in human scalp skin

Despite its limitations, this pilot study presents the first proof of principle that topical triiodothyronine can promote hair growth (i.e. prolong anagen) and can stimulate the intrafollicular production of a potent hair growth factor (fibroblast growth factor 7/keratinocyte growth factor) in intact human scalp skin ex vivo; that is, directly in the human target organ. We also show that the simple, clinically relevant vehicle we have developed and tested facilitates the topical, hair follicle-targeting delivery of thyroid hormones through an intact epidermal barrier.