“Replacing the oestrogen that your body is no longer producing with the versions found in conventional HRT is like replacing parts designed for a Chevvy with those made for a Mercedes,”
So says Dr Jonathan Wright, Medical Director of Tahoma Clinic in Washington USA, and a long-time advocate of what are known as bioidentical hormones. “They may be roughly the same, but with both engine parts and biology, very precise measurements matter.”
The idea of bioidentical hormones has been attracting a lot of attention in America, especially since actress Suzanne Somers published a best-seller on their benefits. However claims that they are safer or more effective has been dismissed as “marketing” by the American drugs authority, the FDA.
Here in the UK, the situation is typically much more low-key. There’s been far less publicity about them, although a small but growing number of women have been taking them.
Several brands are available on the NHS, however most GPs are reluctant to prescribe them, saying there is no evidence they work. So what exactly does it mean to say that a hormone is bio-identical?
A regular HRT pill contains oestrogen – the hormone that promotes growth so it’s good for skin and hair, lifts depression, controls hot flashes – along with a synthetic progestin, not progesterone as that’s the hormone that’s produced to prepare your body for pregnancy.
Not all oestrogens are equal
Just to complicate matters oestrogen in the body comes in three varieties – oestrodial, oestrone and oestriol. Not only that but they come in very different proportions.
Oestriol is the weakest and pre-menopausal women normally have lots of it; it makes up about 90 per cent of the total amount. The next most abundant is oestradiol, the most potent one, at around 7 per cent, followed by oestrone at 3 per cent.
But in regular HRT, the oestrogen part doesn’t come in anything like those proportions. One of the most common brands is one called Premarin which actually comes from the urine of pregnant mares. Not only are the proportions very different but it also contains extra horse oestrogens.
Oestrone shoots up from being the least to the most abundant at 75 per cent; next comes oestradiol which, together with two other horse oestrogens, makes up between 6 and 15 per cent. And finally you get 5 to 19 per cent of another horse hormone called equilin. Very different.
Even in hormones which are molecularly very similar, the difference in effect can be huge. One way of summing up the difference between men and women would be that it is the difference between early exposure to testosterone or oestrogen. But the oestrogen oestrodial is actually more like testosterone than it is like Premarin. Yet women are advised that premarin is a suitable replacement for oestrogen.
Why progesterone is key
The other hormone that’s found in regular HRT is called a progestin. These are non-identical versions of the hormone progesterone. During menopause the amount of progesterone in your body drops more dramatically than oestrogen, to almost zero.
Non-identical progestin is added to regular HRT to reduce the risk of womb cancer which is raised by giving oestrogen on its own. You can get an idea of how big the difference is between bioidentical progesterone and progestin from their effect on pregnancy.
Progesterone is the hormone that the body makes to support pregnancy – it’s used as part of infertility treatments – while progestin raises the risk of congenital abnormalities and miscarriage.
According to NHS Direct, other progestin side effects include breast tenderness, headaches, mood-swings and depression. The main side-effect of progesterone is sleepiness.
Examining the evidence
So are the identical versions of these hormones safer and more effective? It’s an attractive idea that makes sense but what’s the evidence? At the moment if you want it proved in a big trial comparing the two, then it’s not there.
But there are plenty of people who find that, quite apart from the possible long-term risks of regular HRT, that it just doesn’t agree with them, while a switch to bio-identical HRT (BHRT) transforms them.
Women need both progesterone and oestrogen throughout their lives: oestrogen helps keep skin supple and moisturised and gives us our rounded, feminine shape. Progesterone is vital to protect against excess oestrogen and avoid risks such as heart disease, strokes and osteoporosis.
The key is to have these hormones in balance but at menopause women often put on weight and oestrogen is produced in the fat cells and so you end up with an excess of oestrogen over progesterone – this is oestrogen dominance.