Perimenopause can start at 38 — and hair is usually the first thing to notice

18 August 2026  ·  7 min read  ·  Reviewed for accuracy September 2026

There is a gap in what women are told about their hormones. Pregnancy and birth are covered in detail. Menopause, at last, is being talked about. The ten years in between — the late thirties and forties, when oestrogen begins its slow, uneven decline — are barely mentioned, and it is exactly the decade in which most mums notice their hair change.

What perimenopause actually is

It is not a switch. It is a slow fall in oestrogen, with fluctuations, that begins on average around 45 but commonly starts in the late thirties. Cycles are usually still regular at the start. Sleep may change, mood may change, and hair very often changes — because the follicle is one of the most oestrogen-dependent tissues in the body and it responds to a fall that no blood test will reliably pick up yet.

Why hair goes first

Oestrogen does three things for a follicle. It shields it from DHT, the androgen that miniaturises hair. It keeps the tiny blood vessels that feed the follicle open. And it keeps the growth phase long. As oestrogen falls, all three weaken together: DHT gets in, supply narrows, and the growth phase shortens. The result is finer hair, a wider parting, softening corners and more in the brush — years before anyone would think to say the word perimenopause.

The follicle does not wait for a diagnosis. It responds to the hormone level it is actually seeing.

Why it is worse for mums

Every woman goes through this decline. The difference for mums is that their follicles have already been through a much sharper version of it: the drop after each baby. Follicles that went dormant in the postnatal window and never properly restarted are the least resilient when the slow decline arrives, which is why so many women describe their hair going “again” at 38 or 41, in the same places it went after the children.

What about HRT?

If you are offered HRT for other symptoms, it restores some of the oestrogen shield and many women see their hair stabilise. It is not designed for hair, it does not act on DHT at the follicle directly, and it does not by itself restart follicles that have already gone quiet. Women on HRT who are still waiting for their hair to come back are a group I see often, and the reason is that permission and instruction are different things: HRT gives resting follicles permission to grow; it does not send the signal.

What to do with this

First, rule out iron and thyroid. Then read the pattern. If it is the hormonal, follicle-level thinning described here, the good news is that it has a mechanism and the mechanism can be addressed at the scalp, without waiting for a diagnosis that may be years away.