Topical L-Thyroxine: The Cinderella Among Hormones Waiting to Dance on the Floor of Dermatological Therapy?

The document reviews the potential of topical L-thyroxine (T4) in dermatological therapy, particularly for wound healing and hair growth. It highlights the role of thyroid hormones in skin and hair follicle biology, including their impact on gene expression, keratinocyte differentiation, melanogenesis, and stem cell function. The authors suggest that T4 can promote wound healing by enhancing keratinocyte proliferation and angiogenesis, and may also have anti-aging effects on skin, counteract steroid-induced skin atrophy, and stimulate hair follicle stem cells. However, they caution against long-term use due to risks of systemic toxicity and carcinogenicity, advocating for short-term applications and further research into its efficacy and safety. Despite regulatory and financial challenges, the authors encourage dermatologists to consider off-label use of topical T4 for certain skin conditions.