Neuroendocrinology of the hair follicle: principles and clinical perspectives

Abstract

The human hair follicle (HF) is an exquisitely hormone-sensitive mini-organ that undergoes cyclical remodeling. It is also a source and target of numerous neurohormones, neuropeptides, and neurotransmitters that regulate HF growth, pigmentation, remodeling, immune status, stem cell biology, and energy metabolism. Indeed, organ-cultured human scalp HFs can be utilized to identify 'novel' clinically relevant functions of major neuromediators. This is pertinently illustrated by the discoveries of: (i) thyrotropin-releasing hormone (TRH) as a hair growth and pigmentation stimulator; (ii) TRH and thyrotropin (TSH) as potent promoters of mitochondrial activity and regulators of keratin expression; and (iii) prolactin as an epithelial stem cell modulator. Thus, HF neuroendocrinology affords insights well beyond hair growth and dermatoendocrinology, uncovering new translationally relevant neuroendocrinology principles and novel therapeutic targets.

Keywords: CRH; TRH; TSH; mitochondria; prolactin; skin.