All in the hormones?

Vivienne Parry, writer, broadcaster and science enthusiast, doesn’t seem to be too concerned about offending the new conformism. Reminiscing on her early teenage years – when she towered above her male dancing partners – she declares: ‘Thank God my mother smoked 40 cigarettes a day during pregnancy, or else I would have been 6 foot 3.’

In her new book The Truth about Hormones, published this week, Parry seeks to provide some ‘perspective and sanity’ on the discussion about hormones. We know that both natural and manmade chemicals with hormone-like actions are ubiquitous. They are in the water we drink, the air we breathe, the food we eat and ‘in the very fabric of our daily lives, in cosmetics, plastics and household chemicals’. These endocrine disruptors – or ‘gender benders’ as they are commonly called – can block or disrupt the actions of human hormones.

This may sound scary, but as Parry tells me, ‘every mouthful of food that we have has some “endocrine disrupting” activity – without harm. Our bodies are evolved to have a large amount of “endocrine disruption” going on’. She explains that plant foods contain at least 12,000 chemicals – produced for structural, attractant, chemoprotective and hormonal purposes. Cabbage contains 49 natural pesticides. Although eating cabbage may inhibit the action of oestrogen, Parry says ‘such food has been part of the human diet for centuries and common sense suggests that we need not fear them’.

Some chemicals with oestrogen activity, such as phthalates, were banned in Europe in 2004. However this chemical is ‘five orders of magnitude [100,000] times less potent than the oestrogen in your own body, and a hundredfold less potent than the phytoestrogens found in food which you eat all the time’. Parry says: ‘We worry about the tiniest levels of hormones, believing they may cause major threat – when we have got walloping levels of hormones onboard internally. It doesn’t make sense.’

She finds it rather curious that some natural hormone disruptors are viewed as good while synthetic chemical disruptors are viewed as bad – especially given that ‘the [scientific] work that has been done shows that natural and synthetic chemicals turn on exactly the same genes’.

Synthetic chemicals are blamed for everything from the falling age of puberty and declining sperm counts to increasing rates of testicular and breast cancers. But take the age of puberty: falling from around 17 years of age in the mid-nineteenth century to around 11 years of age today. This may seem ‘unnatural’ to us – that 11-year-old girls are developing breasts, for instance. But as Parry says, ‘part of the reason for this is simply that we are better fed and are healthier. It is curious thing, isn’t it? People want to say that chemicals are all terrible and horrible, and we are all going to hell in a handcart, but at the same time we are living longer than ever before – which is kind of an inconvenient fact.’

The study of hormones has a relatively short history: it wasn’t until 1905 that the word ‘hormone’ was first coined. Most people (including myself) know little about hormones, other than being able to name a few – such as testosterone, oeststrogen or adrenalin. For those who want a better understanding, Parry’s opening chapter, ‘A bluffer’s guide to hormones’, is an accessible and fun read. She explains that hormones are one of the body’s two great communication systems. The nervous system carries messages from the brain that are transmitted throughout the body by electrical stimuli, while the endocrine system – the hormone system – is much slower, and uses the blood as its medium for communication, and chemicals – hormones – as its messenger.

We are shown how hormones rule our internal world: controlling our growth, metabolism, weight, water balance, body clock, fertility and much more. Parry criticises ‘hormone determinism’, arguing in The Truth about Hormones that ‘hormones are just part of what you are and there’s more to human life than the endocrine system, magnificent though it is’. But she herself seems to veer towards this when it comes to the murky subjects of sex and attraction, claiming that hormones ‘are busily brokering marriages behind the scenes’. In the same chapter she writes, ‘Free will? I don’t think so, madam. We’re talking sexual chemistry here with your brain playing Cupid, and your hormones providing the arrows’.

Endocrinology clearly can tell us much about how our bodies work, and provide insights into why certain behaviours are selected for through evolution. But hormones do not control us. Neither, of course, are we in control of our hormones. As Parry states ‘hormones to some extent work behind our backs’. Even though most women don’t know when they are ovulating, research has found that men do seem to be able to tell. Studies have shown, Parry explains in the book, that ‘simulated ovulation scents send [men’s] testosterone levels soaring’. So subconsciously men’s brains are picking up olfactory signals from women – which would make sense in human evolutionary terms. But does that mean that the study of hormones can tell us about love, romance or marriage – who we fall for, whether or not we pursue an initial attraction or decide to commit to a person?

When Parry discusses the phenomenon of adolescence she again emphasises the biological roots of ‘living in a universe of one’, arguing that: ‘Teenagers are trapped in limbo – neither children nor adults: an excruciating mix of vulnerability and potential, which by turns engages, inspires and alienates adults.’ She continues: ‘It is tempting to believe – indeed, it has always been assumed – that [teenage] behaviour is entirely hormone driven. After all, aren’t teenagers hormones on wheels?’

Hormones themselves aren’t seen as the problem. ‘There is no consistent relationship between normal circulating testosterone levels and violence in teenagers.’ Instead, she tells me, it is the process of neurological maturation that is responsible for much of the behaviour that was classically attributed to hormones – ‘teenagers are disabled by the brain changes that are going on’.

But adolescence is not a timeless or universal human concept. Youth culture is a relatively recent phenomenon, emerging during the twentieth century. Not all societies have a period of adolescence. In some societies children enter adulthood, with all the responsibilities that entails, in their early teens. Brain changes may have an impact, but it’s unlikely that they alone can explain adolescent behavior.

And surely there cannot be a biological explanation for the expansion of adolescence in Western societies? Parry recognises this. ‘My parents’ generation was pretty much out of the nest and working at 16’, she says. ‘If I get mine out of the nest [she has two adolescent boys] by 25 I’ll be lucky – and that’s probably how most parents feel. That’s partly because of a cultural shift. We want them to stay in education longer – recognising they need this period of adjustment and experimentation at being an adult.’

Although I wouldn’t go along with the claims made in the Truth about Hormones that we ‘are completely in the thrall of [hormones]’, Parry does show the potential of this exciting – and adolescent, I suppose – science that can potentially teach us so much more about ourselves and our bodies.

The Truth About Hormones is published by Atlantic books, 2005. Buy this book from Amazon (UK).