Far from being my crowning glory, my hair has been the bane of my life. But one question has always plagued me: is my problem on my head, or in my head? While I've suspected my hair has been thinning for decades, few people ever believed me and at times I even doubted it myself.

There were years when my hair seemed fuller, when I'd scrunch it into ringlets and delight at its apparent thickness. At other times, particularly in my 30s, I'd fret over the wispy strands at the front of my head or when I saw too much scalp in the mirror.

My friends always reassured me I had a good head of hair. Most of the GPs I saw reacted the same, despite my tears and protestations. I had no bald patches or visible gaps so they'd put it down to stress or would test my iron and thyroid levels, which appeared normal.

Some of my hair loss over the years is easily explained. I developed an eating disorder and recall gathering clumps of hair off my pink bedroom carpet when I was under-eating in my teens.

Weight loss, low iron levels, poor diet and stress, along with thyroid and hormonal imbalances, can all cause hair to fall, trichologists say. Hair needs a healthy diet and a well-functioning endocrine system to flourish.

But diffuse hair shedding linked to weight, anaemia, diet or thyroid problems is temporary, according to Glenn Lyons, the clinical director at the Philip Kingsley Trichological Clinic in London. The hair follicle isn't damaged and the hair grows back automatically or once an imbalance is addressed.

The same goes for hair loss after childbirth or following cancer treatment – in most cases hair is restored. Even with alopecia areata, the sudden hair loss experienced by TV presenter Gail Porter that leaves bald patches, hair often grows back, although the problem can recur.

There is another type of female hair loss, however, that is less dramatic and less visible, but can be incredibly distressing. The hair thins gradually, often over decades, around the top frontal area and extending back to the crown. It can start at any age, is progressive and inherited.

"Genetic hair loss is the only hair loss in which the follicle gradually gets smaller and finer and producers smaller and finer hair until it stops altogether and then you get the thinning," says Lyons.

"It has a massive psychological impact on women because they're balding and thinning in a similar way to the men," adds Lyons, who sees women in their teens to their 80s with the condition. "There isn't a week goes by when we don't get women in tears in here. It affects self-esteem, confidence, quality of life and relationships."

Androgenetic alopecia, as the condition is known, is male hormone-related but isn't caused by too much testosterone. Instead, the hair follicles become sensitive, due to a genetic predisposition, to normal levels of male hormones in a woman's body.

But female hair loss is complex and Dr Hugh Rushton, a Harley Street trichologist, says 72% of women with male hormone-related hair loss are also iron deficient: "The key is to get an accurate diagnosis and to eliminate all other potential factors."

Stress can exacerbate genetic hair loss since the adrenal or stress glands secrete male hormones into the body, says Lyons. Polycystic ovaries can also accelerate the condition, and genetic hair loss will worsen in menopause unless treated as oestrogen levels drop.

I've had some ovarian cysts and have suffered with erratic eating, low iron and stress. But I always suspected there was something more to my thinning hair. The idea that it's genetic is finally making sense.

My mother's hair has been thinning for years, and her mother's did too. The gene can be passed down by either or both parents, and it can affect just one sibling – my brother has a great head of hair.

Fortunately for women, female pattern baldness is less severe than the male variety.

Lyons treats patients with scalp drops that aim to stop male hormones or androgens from damaging the follicles. For some women, trichologists recommend oral contraceptives, but only those with anti-androgens. Some contraceptives exacerbate hair loss, as do some hormone replacement therapies.

Dermatologists may prescribe the over-the-counter drug minoxidil for the scalp, but Lyons says lotions need to contain anti-androgens to fight genetic hair loss.

The correct treatment can restore some of the hair if the follicles are still alive but if they've died, the hair won't grow back, experts say. Existing hair can be preserved, however. The key, for the sake of a woman's sanity and self-esteem, is to catch the condition early – some women can lose up to half their hair before they even notice.

In my case, it's clear I've lost some of my hair for good. I have to keep it short, it feels fine and wispy and I can see too much scalp on the top. But perhaps I can do something about what's left. And even if I am losing my hair, at least now I know I'm not losing my mind.

Hair loss facts

Telogen effluvium – general shedding from all over the head. We typically lose some 100 hairs a day but sometimes shedding accelerates due to stress, illness, medication or hormones. Hair generally grows back within six months.

Androgenetic alopecia – in women, hair generally thins in the top, frontal area, just behind the hair line, but stays thick at the back. An enzyme causes conversion of the male sex hormone testosterone to another hormone, dihydrotestosterone (DHT), causing the hair follicles to produce thinner hair until they stop.

Alopecia areata – an autoimmune disease that affects up to 2% of the population. It causes round patches of hair loss and can lead to total baldness. In many cases, the hair regrows.

There are about 50 different hair loss disorders among men and women. For more information, visit nhs.uk/conditions/hair-loss.

• National Hair Loss Awareness Week is promoted by the Institute of Trichologists and runs until 6 February