Head hair comes in many colours, shapes and sizes, and hairstyles are often an expression of personal style or cultural identity.

Many different genes determine our hair texture, thickness and colour. But some people’s hair changes around the time of puberty, pregnancy or after chemotherapy.

So, what can cause hair to become curlier, thicker, thinner or grey?

Curly or straight? How hair follicle shape plays a role

Hair is made of keratin, a strong and insoluble protein. Each hair strand grows from its own hair follicle that extends deep into the skin.

Curly hair forms due to asymmetry of both the hair follicle and the keratin in the hair.

Follicles that produce curly hair are asymmetrical and curved and lie at an angle to the surface of the skin. This kinks the hair as it first grows.

The asymmetry of the hair follicle also causes the keratin to bunch up on one side of the hair strand. This pulls parts of the hair strand closer together into a curl, which maintains the curl as the hair continues to grow.

Follicles that are symmetrical, round and perpendicular to the skin surface produce straight hair.

Life changes, hair changes

Our hair undergoes repeated cycles throughout life, with different stages of growth and loss.

Each hair follicle contains stem cells, which multiply and grow into a hair strand.

Head hairs spend most of their time in the growth phase, which can last for several years. This is why head hair can grow so long.

Let’s look at the life of a single hair strand. After the growth phase is a transitional phase of about two weeks, where the hair strand stops growing. This is followed by a resting phase where the hair remains in the follicle for a few months before it naturally falls out.

The hair follicle remains in the skin and the stems cells grow a new hair to repeat the cycle.

Each hair on the scalp is replaced every three to five years.

Hormone changes during and after pregnancy alter the usual hair cycle

Many women notice their hair is thicker during pregnancy.

During pregnancy, high levels of oestrogen, progesterone and prolactin prolong the resting phase of the hair cycle. This means the hair stays in the hair follicle for longer, with less hair loss.

A drop in hormones a few months after delivery causes increased hair loss. This is due to all the hairs that remained in the resting phase during pregnancy falling out in a fairly synchronised way.

Hair can change around puberty, pregnancy or after chemotherapy

This is related to the genetics of hair shape, which is an example of incomplete dominance.

Incomplete dominance is when there is a middle version of a trait. For hair, we have curly hair and straight hair genes. But when someone has one curly hair gene and one straight hair gene, they can have wavy hair.

Hormonal changes that occur around puberty and pregnancy can affect the function of genes. This can cause the curly hair gene of someone with wavy hair to become more active. This can change their hair from wavy to curly.

Researchers have identified that activating specific genes can change hair in pigs from straight to curly.

Chemotherapy has very visible effects on hair. Chemotherapy kills rapidly dividing cells, including hair follicles, which causes hair loss. Chemotherapy can also have genetic effects that influence hair follicle shape. This can cause hair to regrow with a different shape for the first few cycles of hair regrowth.

Hormonal changes as we age also affect our hair

Throughout life, thyroid hormones are essential for production of keratin. Low levels of thyroid hormones can cause dry and brittle hair.

Oestrogen and androgens also regulate hair growth and loss, particularly as we age.

Balding in males is due to higher levels of androgens. In particular, high dihydrotestosterone (sometimes shortened to DHT), which is produced in the body from testosterone, has a role in male pattern baldness.

Some women experience female pattern hair loss. This is caused by a combination of genetic factors plus lower levels of oestrogen and higher androgens after menopause. The hair follicles become smaller and smaller until they no longer produce hairs.

Reduced function of the cells that produce melanin (the pigment that gives our hair colour) is what causes greying.

Theresa Larkin, Associate professor of Medical Sciences, University of Wollongong

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Menopause is having a bit of a moment, with less stigma and more awareness about the changes it can bring.

A recent senate inquiry recommended public education about perimenopause and menopause, more affordable treatments and flexible work arrangements.

But like many things in life the experiences of menopause are on a continuum. While some women find it challenging and require support, others experience some physical and emotional benefits. These are rarely reported – but we can learn from the research available and, importantly, from people’s lived experiences.

Here are four changes to look forward to once you reach menopause.

1. No more periods or related issues

Menopause is considered “complete” 12 months after the final period of a woman (or person assigned female at birth) who previously menstruated.

Perhaps unsurprisingly, the benefit at the top of the list is no more periods (unless you are taking hormone therapy and still have your womb). This can be particularly beneficial for women who have had to manage erratic, unpredictable and heavy bleeding.

At last, you don’t need to keep sanitary protection in every bag “just in case”. No more planning where the bathroom is or having to take extra clothes. And you’ll save money by not purchasing sanitary products.

There is also good news for women who have had heavy bleeding due to uterine fibroids – common benign gynaecological tumours that affect up to 80% of women. The evidence suggests hormonal changes (for women not taking hormone therapy) can lead to a reduction in the size of fibroids and relieve symptoms.

Women who suffer from menstrual migraine may experience an improvement in migraines post-menopause as their hormonal fluctuations begin to settle – but the timeframe for this remains unclear.

For some women, no more periods also means more participation in social activities from which they may have been excluded due to periods. For example, religious activities or food preparation in some cultures.

2. Getting your body and your groove back

Throughout their reproductive lives, women in heterosexual relationships are usually the ones expected to be proactive about preventing pregnancy.

Some post-menopausal women describe a re-emergence of their sexuality and a sense of sexual freedom that they had not previously experienced (despite contraceptive availability) as there is no longer a risk of pregnancy.

A participant in my research into women’s experiences of menopause described the joy of no longer being child-bearing age:

I’ve got a body back for me, you know, coz I can’t get pregnant, not that I haven’t enjoyed having [children] and things like that and it was a decision to get pregnant but I feel like, ooh my body isn’t for anybody now but me, people, you know?

For women who have chosen to be child-free there may also be a sense of freedom from social expectations. People will likely stop asking them when they are planning to have children.

3. A new chapter and a time to focus on yourself

Another participant described menopause as an unexpected “acceleration point” for change.

Women told us they were more accepting of themselves and their needs rather than being focused on the needs of other people. Researchers have previously tracked this shift from “living for others” to “a life of one’s own”.

Some women find the strength of emotions at this time a challenge, whereas others find their potency can facilitate liberation – enabling them to speak their minds or be more assertive than at any other time in their lives.

4. Increased self-confidence

A new sense of liberation can fuel increased self-confidence at menopause. This has been reported in studies based on in-depth interviews with women.

Confidence boosts can coincide with changes in career and sometimes in relationships as priorities and self-advocacy transform.

Life on the other side

It can be hard to think about what is good about menopause, particularly if you are having challenges during perimenopause – but these can get better with time.

In cultures where women are valued as they become older, women describe themselves as positively contributing to the community. They find they gain power and respect as they age.

We need to work towards more positive societal attitudes on this front. Our bodies change across the lifespan and are remarkable at every stage, including menopause.

Yvonne Middlewick, Nurse, Lecturer & Director of Post-graduate Studies in the School of Nursing and Midwifery, Edith Cowan University

This article is republished from The Conversation under a Creative Commons license. Read the original article.