FROM thinning locks to a dry scalp, hormones can play havoc with your hair. Consultant trichologist Eva Proudman tells Alex Lloyd what your mane reveals.

EXCESS SHEDDING

OESTROGEN, the main female sex hormone, plays an important role when it comes to hair growth. At any one time, around 85 per cent of the hair on our head should be in the growing phase – for which high levels of oestrogen are needed – while 15 per cent is resting, shedding or regenerating. So when your oestrogen levels drop, as a result of ageing, the menopause, excess exercise or dieting, or some auto-immune conditions, so does your level of hair growth and more enters the shedding phase.

When pregnant, your oestrogen levels rise so much that your hair jumps to being 90 per cent in the growth phase and often looks fabulous. But once you give birth, this level falls and your hair suffers as a result.

GREY HAIRS

LOSS of hair colour is a natural part of ageing, as your levels of pigment drop due to reduced production of melanin. Melanin is not a hormone itself but is regulated by the alpha-melanocyte-stimulating hormone.

Oestrogen plays a role in it too. But ageing can lead to decreased levels of these hormones, meaning less melanin is produced to colour the hair. Certain autoimmune conditions can attack the sites in the hair where the melanin is produced too. But the old saying is true – stress can also turn hair grey. When you have more cortisol – the main stress hormone – your body goes into “fight or flight” survival mode and channels nutrients to essential cells such as muscles.

Anything non-essential, like hair, is bypassed. No matter how healthy your diet, failing to keep your stress levels in check will have an impact.

FACIAL HAIR

STRAY hairs on your chin and upper lip, as well as developing sideburns, are common in women and many find it distressing. This is a sign of high levels of testosterone and a by-product called dihydrotestosterone (DHT), one of the sex hormones.

Men need it to develop male characteristics but women also produce it and it can lead to excess hair growth on the body. An increase in testosterone normally affects women as they hit puberty and it rises and falls throughout their cycle, but it is balanced by other hormones.

During the menopause, that balance can become skewed. Testosterone levels can also increase when you have a tumour on your ovaries or adrenal glands. Higher testosterone is also a symptom of polycystic ovary syndrome, so hair growth could be a sign to visit your doctor.

BALD PATCHES

IT’S not just men who can develop baldness as they age.

Female pattern baldness – known as androgenetic alopecia – is hereditary and shows up as a wider centre parting that radiates out from the crown. Carriers have a genetically determined shortening of the growing phase of the hair ­lifecycle, which becomes more obvious later in life as levels of the oestrogen that regulates this process drop.

The hormonal changes of menopause also have a second detrimental effect. Less oestrogen allows testosterone to get more bossy and its sidekick DHT (dihydrotestosterone) is known to bind to hair follicles, causing them to shrink and die. Raising oestrogen levels can suppress it, and Hormone Re­placement Therapy can help in perimenopausal and menopausal women.

THINNING HAIR

HORMONAL changes can also have an indirect impact on your hair due to their effect on the nutrients in your body.

Sometimes, thinning and shedding of hair can be down to the body depleting its nutrient stores. During perimenopause, women find their monthly cycles become more frequent or heavier, which can reduce iron levels.

This iron deficiency results in levels of ferritin – the protein in blood that stores iron – dropping and a lack of red blood cells being created to carry oxygen around the body. In this situation, your body will channel ­oxygen to the major organs instead of the hair, which is seen as non-essential. Be wary of crash diets, too.

Women often put on weight during the menopause, but if you start a fad diet to shake off these excess pounds, it has a further effect on your nutrients and your hair. It’s a double whammy.

DULL COLOUR

IF your locks have lost their lustre, it could ­signify a thyroid problem.

Your pituitary gland produces thyroid stimulating hormone (TSH), which tells the thyroid gland how much of fellow hormones triiodothyronine (T3) and thyroxine (T4) to make. High levels of TSH indicate an underactive thyroid, which leads to functions running too slow.

Hair becomes dull, slow- growing and brittle. You may also get thinning eyebrows. This dullness is because one of the functions to slow is production of the skin’s natural oil, sebum, meaning hair loses shine.

However, in the case of low levels of TSH and an overactive thyroid, where functions run too fast, sufferers will notice increased shedding. Medication can control the levels.

COLOUR CHANGE

WE all have our own unique hair tones and shades – which is also reflected in our individual reactions to hormonal changes.

Hormones can and do affect hair colour both on natural and dyed locks. Progesterone and cortisol can trigger changes in shade, but oestrogen is the dominant factor. It can determine a higher content of melanin – the substance that produces pigmentation – in female hair. For example, one member of the melanin family – eumelanin – is responsible for dark colours in your hair, skin and eyes. A surge of oestrogen could lead to more eumelanin, making hair darker and more ­difficult to dye. But less eumelanin will turn hair lighter and make chemical colouring easier.

If hair dye is applied and hormone fluctuations trigger a hot flush, the colour can process more quickly.

GREASY OR DRY SCALP

MEN tend to have naturally greasier hair than women.

This is because testosterone – the main male sex hormone – is part of a group of hormones called androgens and when these surge, there is increased production of sebum, an oily substance in the skin. This is why teenagers going through puberty suffer with greasy hair – and women can experience the same ­problem during perimenopause and menopause, as their hormone levels change.

If your hair is thinning as well, it has less opportunity to absorb the excess oil, so greasy hair might be more obvious in older women. Menopausal women might also get the opposite issue and suffer with a dry and itchy scalp.

Oestrogen stimulates the body’s production of oils, which keeps the scalp naturally moisturised. Therefore declining oestrogen can cause less oil production, leading to dryness and itching.