Why does hair loss happen?

The loss of hair is an extremely prevalent phenomenon. Here in the UK, it's estimated that, by age 50, 85% of men and 40% of women will experience some form of pattern baldness. So what is happening to the hair cycle that Desmond outlined to cause us to lose our hair? I’ve been speaking with consultant dermatologist Justine Hextall.

Justine - If you've lost hair, then that means that something's changing about the hair follicle. Now, it might be, for example, one of the most common causes of hair loss is what we call androgenetic alopecia, or male or female pattern baldness. And what happens is, over time, the hair follicle becomes miniaturised, becomes smaller, so the hair that it produces is no longer this thick, what we call terminal hair, but it's very fine, vellus hair. The follicle eventually becomes dormant, and you get some loss of hair in those areas. And that's what we call male pattern or female pattern baldness. But there can be other causes, you know, of hair loss. So, for example, your body might produce an immune response against the follicle, as in alopecia areata, or you might have inflammation around the follicle, so there might be an inflammatory process, which is effectively destroying the follicle, so you get this scarring alopecia, and this may be caused by infection or inflammation, and that's where the follicle's actually destroyed, and that hair is very hard to get back.

Chris - On the first of those that you just mentioned, androgenetic alopecia, the clue's sort of in the name, isn't it? Androgen, male hormones, because it tends to affect men mostly, but not exclusively, do women get this as well?

Justine - They certainly do, and I think people don't realise that. So, two-thirds of women at the age of 50 will have experienced some hair loss. So, obviously, we see it much more in men, but women will have it, to a lesser extent, maybe less obvious. So, yes, androgenetic alopecia in men, and that's to do with the hair follicles becoming smaller, and that's through a hormone called dihydrotestosterone, and that's an active form of testosterone. Now, we have these androgen receptors in men, specifically, at the front of the scalp, mostly concentrated, and also on the back, on the centre of the crown of the scalp, and that is why we tend to see hair loss in the front of the scalp. So, you start to get this regression of the hair at the front, but also on the crown, because dihydrotestosterone focuses on those androgen receptors, and it causes them to shrink, and they get smaller, and the hair starts to disappear in those areas.

Chris - Do we know why that should happen? Why should a ubiquitous-in-the-body hormone cause a pattern of hair loss like that?

Justine - Heritability is quite high. The genetics in men is probably about 90%, so it depends which genes you've inherited, and it's not about one gene, it's polygenetic. So, there's one important gene called the androgen receptor gene, which we inherit on the X chromosome, so men will get that from their mothers, and because men only have one X chromosome, it's kind of like sitting there, all the cells then will have that gene, and if that's a gene which is going towards hair loss, then it's going to be expressed more in men, for example, than it is in women. But it's not just that X chromosome, there are other inheritances from the father and the mother.

Chris - How does it happen in the women then? Is it that they do get exactly the same mechanism, but because they have less testosterone, it just takes longer?

Justine - Well, the distribution of the androgen receptors in women is more diffuse, it's not in those areas, but there are other hormones in play. So, for example, oestrogen will protect the hair follicles from hair loss, so until someone goes through menopause, there's a protective element. Women are more susceptible to certain environmental factors as well, stress and other hormones, so it's just not so direct, it's more complicated in women.

Chris - Now, you mentioned stress. This is often cited as a cause of either prematurely going grey or premature balding. Is that just someone fantasising, saying, well, I got stressed and they're sort of attaching a significance to a coincidence? Or is there a mechanism behind that as well?

Justine - No, as I said, with epigenetics, certain genes can be switched on through stress, so if you have a genetic propensity towards losing your hair or androgenetic alopecia, say in a man, but you're also in a stressful environment, it can switch those genes on. But also, when we're stressed, and that might be mental stress, you know, with work, or it might be, for example, physical stress, like an operation or certain medications, they can create something called telogen effluvium. So our hair has a growth cycle, anagen, and then it has a catagen cycle, and then what we call telogen, where it starts to rest and then drop. And what happens with telogen effluvium, which can be switched on by stress, is the hair cycle gets pushed towards telogen, where there's increased drop. But because there's a gap of about three months from that being switched on to noticing the hair loss, people don't always make that association between that period of stress or illness and that sudden, diffuse loss of hair.

Chris - Is that form of hair loss permanent? Because if you've got the androgen-related hair loss, in male pattern baldness, for example, you're probably not going to get that hair back, are you? But if you go through a period of extreme stress, is that also irreversible, or as soon as the stress subsides, your hair comes back?

Justine - Usually, when that period of stress disappears, then the hair cycle shifts back to a longer anagen cycle and less of a hair drop. But some people can develop what we call chronic telogen effluvium, so it can be ongoing. So it's important to look at those drivers.

Chris - And if I look at my mum and my mum's dad, and I find, oh dear, it looks like the genetic legacy being handed to me is going to be one that I'm going to prematurely bald. Is there anything, as a man, I can do about that?

Justine - Yes, I think there is. I mean, first of all, think about your general health. As I said, diet, stress, certain factors will have an influence on our hair health. That's really important. But also, you might want to intervene a bit earlier on. So you might want to start using something like minoxidil. Minoxidil is used topically and sometimes orally. And this is a medication actually for blood pressure, which vasodilates the vessels. And they found that in their studies on blood pressure, people were getting hair growth. And it seems that minoxidil can help with hair growth and to start to stop some of that process with androgenetic alopecia. You get increased hair growth, so you get back more towards the anagen phase. The hair becomes slightly thicker and you start to reverse some of that miniaturisation of follicles. There are other medications. People can have things like finasteride. That is a drug which blocks the enzyme 5-alpha reductase 1, which pushes testosterone to that active form of dihydrotestosterone, which affects the follicle. So you can use that drug. That is FDA approved, but it can have side effects. Some of them get sexual dysfunction. They can get noticeable breast development. There's even anecdotal discussion around possible lowering of mood. So it is a drug which works, but not without side effects. So you need to be carefully monitored.