Armand Marie Leroi

Mutants

Cretinism is a global scourge. In 1810 Napoleon Bonaparte ordered a survey of the inhabitants of the Swiss canton of Valais; his scientists found four thousand cretins among the canton's seventy thousand inhabitants. The location is telling. As the Taron Valley lies in the foothills of the Himalayas, so Valais lies at the base of the Alps. Swiss cretins have not been spotted since the 1940s, but a belt of cretinism still tracks most of the world's other great mountain ranges: the Andes, the Atlas, the New Guinea highlands, the Himalayas. What these areas have in common is a lack of iodine in the soil. People and animals alike rely on their food for a ready supply of iodine, but in many parts of the world, especially at high altitude, glaciation and rainfall have leached most of the iodine out of the soil so thai the very plants are deprived. Cretinism is caused by a diet that contains too little iodine. Globally, about one billion people are at risk of iodine deficiency; six million are cretins.

In the Gothic cathedral of Aosta, ten kilometres south-east of Mont Blanc, the choir stalls are decorated with portraits of cretins. They were carved to keep their fifteenth-century viewers mindful of the unpleasantness of Eternal Torment: a local version of the fabulous creatures and demonic creatures of misericords elsewhere. Many of the cretins have a curious feature: their necks are bulging and misshapen; one even has a bi-lobed sack of flesh hanging from his throat large enough to grasp with both hands. Just over a hundred years after Aosta Cathedral was built. Shakespeare would write in The Tempest: 'When we were boys/Who would believe that there were mountaineers/Dew-lapp'd like bulls, whose throats had hanging at them/Wallets of flesh?'

The Aosta cretins and Shakespeare's mountaineers were goitrous. Goitre is an external manifestation of an engorged thyroid, a butterfly-shaped organ located just above the clavicles. Like cretinism, it is a sure sign of iodine deficiency. When first discovered in i6n, the thyroid was thought to be a kind of support for the throat, a cosmetic device to make it more shapely. In fact it is a gland that makes and secretes a hormone called thyroxine. The thyroid needs iodine to make this hormone, and should iodine become scarce, the thyroid attempts to restore order by the rather drastic device of growing larger. The result is at first a swollen neck, then a bulging neck, and finally, in elderly people who have lacked iodine all their lives, an enormous bag of tissue that spreads from beneath the chin onto the chest, and that contains vast numbers of thyroid tissue nodules, some of which are multiplying, others of which are dying, yet others of which are altogether spent. In England this is called 'Derbyshire neck'.

A goitre is an ugly but useful thing to have, particularly for a pregnant woman. Thyroxine is yet another hormone, albeit not a protein, that promotes cell proliferation in the bones of foetuses and growing children. It also controls the number of cells that migrate down the growth plate to swell and die before forming bone. A foetus gets the thyroxine it needs from its mother; should it not get enough it is born cretinous. Lack of dietary iodine during childhood can also cause cretinism. And cretinism can also be, albeit rarely, a genetic disease. Many human mutations are known that disrupt the production of thyroxine, its storage, its transport around the body, or its ability to dock to its receptor. There is also a class of mutations more vicious by far than those that simply cause thyroid malfunction. These mutations affect the pituitary. Among the hormones that the pituitary produces is one that controls the thyroid. This hormone, thyrotropin, regulates the way that the thyroid absorbs iodine, the rate at which it manufactures thyroid hormone, and the way it grows and shrinks according to need. The pituitary is the thyroid's check and its balance. Goitre is a witness to its workings. The pituitary monitors the level of thyroid hormone that circulates around the body and, should it perceive a want, begins producing thyrotropin, which then spurs the thyroid to greater efforts-in the extreme, spurs it to make a goitre. Children who have defective pituitaries are dwarfed for want of growth hormone and cretinous for want of thyroxine.

But the vast majority of the world's cases of cretinism are caused by a simple lack of dietary iodine. The tragedy of six million cretins is that the cure and the prevention of the disease is known, and costs next to nothing: it is simply iodised salt. It was the legislated spread of iodised salt in the early twentieth century that eliminated European goitre and cretinism within a generation, so that today these diseases are little more than folk-memories. Indeed, iodine deficiencies are so utterly forgotten in the developed world that outside medical and scientific circles the term 'cretin' exists only as a casual term of abuse. What is more, 'cretin' survives where comparable epithets have been justly banished from decent conversation. The word simply has no constituency, no defenders. Are the Taron of Upper Burma cretins? Is their smallness part of the vast and glorious tapestry of human genetic diversity, or are they merely victims of a peculiar form of high-altitude poverty? Were we to hear that there are no longer tribes of little people in the vertiginous gorges off, the upper Irrawaddy, should we cheer or lament?