Woman: An Intimate Geography (33 page)

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Authors: Natalie Angier

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BOOK: Woman: An Intimate Geography
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10
Greasing the Wheels: A Brief History of Hormones
Every morning I take a little pill that contains thyroxine, a hormone produced by the moth-shaped thyroid gland in the middle of the neck. When I was in my twenties I had Graves' disease, an autoimmune disorder in which the thyroid becomes hyperactive and generates too much thyroxine. I hate going to doctors, and it went undiagnosed for months. I was jittery, anxious, an emotional hacksaw. My heart raced at 120 beats a minute, nearly twice my normal pulse, even when I lay in bed. I had been an athletic woman, but suddenly I lost all my strength and could not walk up a flight of stairs without stopping for a break midway. I ate ravenously and still lost weight, but I looked too sick to elicit compliments on my slimmer figure. My eyes bulged out slightly and lent me the appearance of a tree frog, a symptom that I now recognize in the faces of other Graves' alumnae, like the former first lady Barbara Bush.
I was treated with radioactive iodine, which homed in on the diseased thyroid gland and destroyed much of it. Now I am hypothyroid, making less thyroxine than I need, and so I will have to swallow one of these supplements every day for the rest of my life. It's a dull business. It doesn't change anything about my mood or personality. It doesn't even offer the mild refreshment of other daily rituals, like the brushing of the teeth or the washing of the face.
Yet if I were to stop taking thyroxine, my life would change for the worse. Gradually, over days or weeks, I'd become irritable, depressed, lethargic, and stupid. I'd gain weight, feel cold most of the time, and lose my libido. My heart rate would become slow and irregular, and my blood pressure would rise. Again I'd be sick and at risk of early death; again I'd be crushed by my chemistry.

 

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Thyroxine is not a sexy hormone. It is not what we mean when we talk of being "flooded with hormones" or "high on hormones," as teenagers and lovers are said to be. The hormone family of chemicals is a vast kindred that includes such familiar bio-actors as the sex hormones the estrogens and the androgens and the stress hormones, our private hair-trigger sentries that counsel panic whether it's a lion or a landlord snorting at the door. It includes a host of backstage technicians that tell us we need salt, food, or water, and it includes compounds that we don't normally think of as hormones at all, like serotonin, the famed target of Prozac, Zoloft, and the other perimillennial mood brighteners.
Through my years of dependency on hormones, I became curious about their contours, their edges and their limitations. I wondered why something like thyroxine, which could be so brutal and upheaving when generated in excessive or insufficient quantities, was otherwise so unremarkable, so unilluminating. In taking the right amount of thyroxine, I returned to the status quo of myself, the stable instability that I have known since the onset of sentience, but nothing more. The best I could do was to keep the old version operating. Thyroxine, then, was at once global and narrow. No tissue, not even my brain, was spared from an abnormality of its production, yet it was not me, not the flesh of self or of consciousness. What was going on, then? Hormones have effects, they have failings, they have meanings. Hormones are far more important than most of us realize, but not in the ways that most of us think.
Lately there has been a hormone renaissance, a renewed fascination with these chemical messengers and what they can do for us, say about us, solve about us. Part of the interest is rhetorical fashion. It is fashionable now to ascribe such supposedly male traits as the tendency to swagger, posture, interrupt, and belch in public to testosterone. Men in groups are said to "reek of testosterone," to be "poisoned by testosterone," to be ''caldrons of testosterone." It sounds cute, it sounds clever, and because yes, men do have a fair amount of testosterone, it sounds accurate as well. Hormone humor does not spare women, though, and so gals on a shopping expedition or sharing a cappuccino become "estrogen sinks" or waft "billows of estrogen." It is also fashionable to talk of love hormones, mommy hormones, and even crime hormones.

 

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We want to explain ourselves to ourselves, and hormones look like a clean and quantifiable way to do so, to distinguish male from female, competitor from cooperator, domesticated from feral. We are incorrigible categorizers.
Popular interest in hormones also reflects a revival of interest among the high priests of organizing principles, scientists. There has been an explosion of hormone research unmatched in ferocity since the first hormones were isolated and synthesized more than seventy years ago. Comforting analogies no longer apply. In the past, hormones were talked of as keys, each designed to fit into a specific receptor the metaphorical lock located on different tissues of the body and brain. In so fitting, a hormone would swing wide the door to a defined suite of behaviors and reactions. Now the metaphor has rusted. It turns out that the body offers up multiple locks to the pryings of any given hormone, and sometimes the hormones exert their might without the need for any lock at all. Instead they can ramrod their way through from blood into tissue, or slip in between the cracks, leaving us agog once more at how potent, how exquisite, and how crude these chemical emissaries can be.
Hormones have a music to them, a molecular lyricism that explains why they are potent and ancient: why they work well enough to have merited retention in one form or another through hundreds of millions of years of evolution. Certain hormones are among the things that make us women, and these are the hormones that I will focus on. They are the fashionable hormones: estrogen, progesterone, testosterone, oxytocin, and serotonin. But the hormones are not slaves to fashion. They don't conform to expectations. They hate clichés.
Hormone
comes from the Greek
horman
, which means to arouse, to excite, to urge. This is what a hormone does. It excites. It urges, though sometimes what the hormone urges is a sense of calm, a call to rest. By the classic definition, a hormone is a substance secreted by one tissue that travels through blood or another body fluid to another tissue, whereupon the hormone arouses the encountered tissue to a new state of activity. The thyroid gland secretes thyroxine, which stimulates the heart, the muscles, and the intestines. A follicle on the ovary bursts open and releases a draft of progesterone, which cues the endometrium to fatten. The classicists thought that hormones differ from neurotrans-

 

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mitters, the quick-snapping chemicals such as norepinephrine and acetylcholine that allow brain cells to communicate; but that distinction has begun to disintegrate as researchers have learned that hormones, like neurotransmitters, can alter the texture and disposition of brain cells, making them more likely to fire. Brain cells talk to one another in a
rat-a-tat-tat
of electrical impulses. And so, while it wouldn't be quite proper to call estrogen a neurotransmitter, it would be proper to call it and the neurotransmitters members of a large chemical family of neuromodulators brain inflectors. This reclassification is more than a semantic issue. It affects how we think about our thinking and feeling and being. It also brings the body and brain into synchrony rather than continuing the old distinction that said endocrinologists get the chemistry from the neck down, while the neurobiologists claim the domain of the brain.
A hormone is not only complex, it is small, a desirable feature in a molecule that would act as a bio-troubadour, always in voluble transit. This concision is true regardless of whether the nut of the hormone, its structural core, is built of grease, as the sex hormones are, or of meat, as the peptide hormones such as oxytocin and serotonin are.
Let's take a zoom lens to the sex hormones, also called the sex steroid hormones. The word
steroid
lately has been pluralized into idiocy, so that when we think of steroids we think of anabolic steroids, the drugs that bodybuilders and other athletes take, at their peril, in an effort to inflate their strength and bulk. Such drugs are usually a synthetic version of testosterone, and thus they are steroid hormones, but the class of steroid hormones is much more inclusive and more interesting than locker-room dope.
If you've ever looked at a diagram of a steroid molecule, and if your high school chemistry teacher didn't entirely annihilate your capacity to appreciate molecular aesthetics, you surely appreciated the steroid's rigorous beauty. A steroid is built of four rings of carbon atoms, arranged so they touch each other like mosaic tiles. Those rings lend stability to the hormone; they do not dissolve easily and so will not fall apart in your blood or in the thick sea of your brain. Moreover, the steroid rings are amenable to modification. Decorations can be added to their side, each new flounce changing the steroid's meaning and power. Testosterone and estrogen look surprisingly similar, yet they

 

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differ enough in their minor appendages to communicate quite distinct messages to a recipient tissue.
Steroids are ancient in nature and play communicative roles in many organisms. Molds secrete steroids. A female mold releases a steroid hormone that will induce a neighboring mold to grow the equivalent of male reproductive organs. Once the solicitee has complied with the request and enmaled himself, he releases another steroid hormone into his surroundings, which induces the female to grow toward him. Come and get it! he cries, and she comes, and she gets it. Plants such as soy and yams have steroid and steroidlike hormones, and in fact a diet rich in these phytoestrogens can help palliate some of the symptoms of menopause. Certain species of aquatic insects synthesize the stress hormone cortisol in such high concentrations that they knock out any fish attempting to eat them. Mexican beetles are like walking birth control pills, generating estrogen and progesterone that some scientists suspect are intended to curb the population of their natural predators. Pigs love steroid hormones; during courtship, a male pig will spit on his sow-heart's face and in so doing expose her to a pungent steroid compound that causes her to freeze with rear legs conveniently parted. All of which might help explain the now quaint term
male chauvinist pig
yessir, a bit of spit and the little woman is yours!
There are hundreds, if not thousands, of varieties of steroid and steroidlike hormones in nature. By definition, a steroid hormone is an elaboration of that ubiquitous and unfairly maligned molecule cholesterol. Cholesterol is a steroid in structure, but it is a no-frills steroid and not in itself a communications vehicle. Only with chemical embellishment does it assume the mercurial role of hormone. All steroid hormones in vertebrates are built of cholesterol. The choice of cholesterol as the foundation for these hormones makes sense, because the body brims with it. Even if you never touch cholesterol-rich food such as eggs, oil, and meat, your liver continues to make cholesterol around the clock, and with reason. Cholesterol is an essential component of the plasma membrane, the fatty, protective coat surrounding every cell. At least half of the average cell's membrane consists of cholesterol, much more than half in neurons. Without cholesterol, your cells would fall apart. Without cholesterol, new cells could not be manufactured. There would be no way of replacing the cells of the skin, gut, and immune

 

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system, which die by the millions each day. Cholesterol is the fat of the earth and the fat of the brain.
The steroid hormones, then, are pieces of ourselves, of the skin of our cells. When our cells wish to communicate, they paradoxically turn to the stuff of membranes, the original isolationists. The plasma membrane separates one cell from another, just as a membrane walled off from its environment the mother of us all, the first single-celled organism, some 3.8 billion years ago. The plasma membrane gave birth to selfhood and organismic loneliness. To reconnect, to speak as one cell, one self, to another, there can be no better language than that of the plasma membrane itself.
The word
hormone
wasn't coined until 1905, and the first one wasn't isolated until the 1920s, but people have known about steroid hormones indirectly for millennia, thanks to the external nature of one particular hormone factory, the testicles. Males, including human ones, were the hapless recipients of the first experiments in endocrinology. Game animals were castrated to make their behavior more manageable and their meat tastier. Men were castrated to render them trustworthy. The Old Testament describes the use of eunuchs to guard the consorts of Hebrew kings and princes. Men also were castrated as punishment for sexual crimes or sexual miscalculations. In the twelfth century, Peter Abelard, the great theologian and philosopher, had his testicles excised for having run off with his beloved student, Heloise. Abelard bitterly mourned his stolen manhood and wrote of it in a memoir,
My Great Misfortune
. (For her part, Heloise was sent unscathed to a nunnery, her gonads beyond reach or medieval understanding. Later she rose to prominence as the head of a convent called the Paraclete, founded by her former lover.)
The role of the testicles in cultivating the many changes of puberty also was known for centuries. Boys with promising soprano voices were accordingly gelded before adolescence to prevent their vocal cords from thickening and their pitches from lowering. According to contemporary accounts, the best of the castrati were magnificent to hear, for they combined the sweetness and luster of a woman's timbre with the power afforded by a man's comparatively large lungs. Castration mania reached a peak in the seventeenth and eighteenth centuries, when thousands of parents had their sons orchiectomized in hopes of stardom and

 

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