Table 1.

Hormonal effects on the hair follicle. ⁸

Hormone	Mechanism of action	Impact on hair
Androgens	Action via intracellular androgen receptor in the dermal papilla	Face, axilla, pubic, chest hair: transformation of vellus to terminal hairs
Testosterone and dihydrotestosterone	5‐α reductase inhibitor converts testosterone to the more potent dihydrotestosterone	Scalp hair: inhibitory
Oestrogen	Binding to high‐affinity oestrogen receptors	Impact remains under investigation, but thought to prolong anagen phase and reduce telogen phase
Progesterone	Central action: inhibits LH secretion, which reduces androgen synthesis	Further research is required to understand the impact of progesterone on the hair cycle. Possible action via androgens
	Hair follicle: inhibits 5‐α reductase (reduces conversion of testosterone to dihydrotestosterone)

LH, luteinizing hormone.