Why Does Women's Hair Go Thin?

Female Pattern Hair Loss (Genetics)

The most common cause is female pattern hair loss (FPHL), an inherited condition in which hair follicles gradually become more sensitive to androgens over time. The follicles shrink progressively, producing finer, shorter hairs until eventually they stop producing visible hair at all. The thinning tends to start at the parting and the crown, rather than the receding hairline pattern seen in men.

FPHL can begin at any age but becomes more common from the mid-30s onwards. It accelerates significantly around menopause, when falling oestrogen levels leave androgens with more influence over the follicle.

Hormonal Changes

Hormones play a significant role in the hair growth cycle. Major hormonal shifts can disrupt that cycle and push larger numbers of hairs into the shedding phase than usual. The most common triggers are menopause and perimenopause, pregnancy and the period after birth, PCOS, and stopping or starting hormonal contraception.

In most hormonally-driven cases, treating the hormonal cause directly produces better results than treating the hair loss in isolation.

Nutritional Deficiencies

Hair follicles are among the most metabolically active structures in the body. They need a steady supply of certain nutrients to function properly. Low levels of iron, vitamin D, zinc, vitamin B12 and protein are all associated with increased shedding and reduced hair quality. Iron deficiency is particularly common in women and is one of the more frequently overlooked causes of hair loss. A blood test can confirm whether deficiency is a factor.

Stress and Illness

Physical or psychological stress can push a large number of follicles simultaneously into the resting and shedding phase, a condition called telogen effluvium. This is commonly seen in the weeks or months following a serious illness, surgery, significant weight loss, or a major life event. The shedding can feel alarming when it starts, but telogen effluvium is usually temporary. Once the trigger resolves, the hair typically recovers without intervention.

Thyroid Conditions

Both an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism) can interfere with the hair growth cycle and cause noticeable thinning. Thyroid-related hair loss often affects the whole scalp rather than following a particular pattern. If your GP has not tested your thyroid function, it is worth asking them to do so.

Age

As we get older, the rate of hair growth naturally slows, follicles produce progressively finer hairs, and overall density decreases. This is a normal part of ageing, but it is often compounded by hormonal changes or nutritional factors that can be identified and addressed.