Pro-thyrotropin-releasing hormone (TRH)

As a component of this hypothalamic-pituitary-thyroid axis, it controls the secretion of thyroid-stimulating hormone (TSH) and is involved in thyroid hormone synthesis regulation. Additionally, it functions as modulator of hair growth.

It promotes hair-shaft elongation, prolongs the hair cycle growth phase (anagen) and antagonizes its conclusion (catagen) by TGFB2. It stimulates proliferation and inhibits apoptosis of hair matrix keratinocytes.