When Laura was growing up in a small New England town, her parents and doctors worried that her predicted adult height threatened her future happiness. Laura's tall mother had been teased and embarrassed about her own height at school. When the local paediatrician mentioned that a specialist might be able to stunt Laura's growth and spare her the social pain of towering over boys as an adolescent and men as an adult, her family agreed. A paediatric endocrinologist affiliated with a prestigious US academic medical centre confidently prescribed the synthetic oestrogen diethylstilbestrol in doses 100 times greater than the oestrogen found in today's high-dose oral contraceptives.

Laura obediently took the little coated pills, now commonly known as DES, for about 2 years. But they made her sick and when she reached adulthood and married, she experienced miscarriage after miscarriage that denied her what she most wanted in life—children. When doctors also diagnosed her with a condition that put her at risk of breast cancer, Laura wondered what effects the little pills might have had on her adult health. She didn't know at the time that other tall girls also went on to have reproductive problems after taking diethylstilbestrol and other high-dose oestrogens to stunt their growth, or that there had been concerns about the drug's potential effects on fertility and cancer even at the time her physician prescribed it. Laura didn't know because none of the physicians she consulted as an adult had heard of the treatment she had received as a child; there had been hardly any follow-up studies of these girls once they became adults.

Meanwhile, the culture of the 1950s and 1960s, which had made limiting the height of tall girls seem like such a good idea to parents and to physicians, was changing rapidly by the mid-1970s. Girls who dutifully swallowed pills to try to remain below 5′6″ so that they could qualify for the corps de ballet or become airline stewardesses, or girls who desperately wanted to stay below 5′10″ to improve their chances of finding a husband, suddenly had many more options in life. They could join a volleyball or basketball team, become doctors and attorneys and police officers, run a business, or compete for political office. The medical advice that suggested tall girls invariably risked psychosomatic illness, or were at risk of not only spinsterhood but homosexuality, today seems quaint. No wonder women like Laura have encountered difficulty explaining this medical intervention to disbelieving obstetricians and gynaecologists.

How do medical therapies launched with the best of intentions result in tragedy? The history of treating children for height provides a compelling allegory for modern medicine, in which cures for disease evolve at an ever-quicker pace into treatments for disability, then for disadvantage, then to satisfy the desire for perfection. Over and over, the best and worst motives combined: the concern of parents and children, the desire of doctors to help and to discover, and the potential profits of industry. There have been far fewer incentives to follow up what happened to these children once they became adults.

In the case of the tall girls who received childhood or adolescent exposure to massive doses of oestrogen, none received any ongoing medical observation, despite calls by some doctors in the mid-1970s to follow them for the rest of their lives. Although diethylstilbestrol is no longer used, and the demand for stunting the growth of healthy girls has dropped in recent decades, some tall girls are still prescribed oestrogens to stunt height, especially when parents insist.

The treatment of short children also illustrates how the most promising cures can lead to inadvertent tragedy. In the mid-1980s, the first of what would turn out to be several hundred cases of Creutzfeldt-Jakob disease (CJD) were confirmed in people who, as children, had been given growth hormone derived from human pituitary glands. Paediatric endocrinologists realised some of the pituitary growth hormone they had injected into their young patients might have been contaminated. One doctor described this as the worst experience of her career. She had to inform parents that their sons and daughters, to whom she had given human growth hormone, might develop CJD. She had to advise them there was neither a test nor a cure. Some of these children had been treated for growth hormone deficiency, which would have left them under 5 feet tall as adults, but not all. Some were just short; they had received some of the scarce human pituitary growth hormone experimentally to see whether they, too, could be made taller.

Some countries attempted to draw lessons from the CJD chapter in treating height. In the UK, where the case went to court, the lawyer who represented the victims noted that we never know as much as we think we do; the judge found the Department of Health should have looked into early warnings less lethargically. In Australia, the government assigned a law professor to undertake a lengthy investigation, which produced this among other conclusions: that it is dangerous not to draw some lines between clinical judgment and experimentation, even if the lines are blurry, and that the failure to attempt to draw lines is most dangerous when new technologies are emerging.

With human growth hormone, technology seemed to ride to the rescue, at least of future young patients, with the development of human recombinant growth hormone, which carried no possibility of CJD infection. But doctors and bioethicists quickly realised that the new drug produced its own set of issues. Suddenly the world had as much human growth hormone as it could use, and the pressure was on physicians to decide whether it should simply go to any child whose family demanded treatment and was willing to pay. For the first time, it seemed possible for many people to modify a hereditary trait they had previously accepted.

The pharmaceutical industry had a stake in these decisions as well, of course. One of the first steps it took in the USA was to use its increasing influence on physicians to redefine normal in order to expand its market beyond the few thousand children with classic growth hormone deficiency. After years of rationed cadaveric hormone, many endocrinologists were eager to help more patients grow. By the time the US Food and Drug Administration (FDA) approved biosynthetic human growth hormone (somatropin) in 2003 for the shortest American children—a potential market of half a million to 1·7 million youngsters—the manufacturers successfully argued that hormone levels were irrelevant. They suggested it was unfair to deny the product to children whose bodies produce adequate levels of hormone but who are as short as those with proven deficiency. Implicit in their argument was that being an extremely short child, for any reason, was a recipe for suffering. Yet they also acknowledged that they had no evidence that a treatment that had added, on average, about 4–5 cm, improved quality of life. The only standard for diagnosis they proposed was height outside the normal range in the USA. The pharmaceutical industry in this instance seemed to be helping to define “normal”, which they pointed out was not a fixed standard. “Normal”, a medical scientist for manufacturer Eli Lilly told the FDA's advisory panel, “changes”.

Today there are more treatments for height than ever before, including the hormone insulin-like growth factor-I, and combinations of therapies that manipulate the timing and effects of puberty using drugs developed for treating cancer. Long-term risks remain unknown, as do long-term benefits. Height prediction is still uncertain, as is a child's ultimate response. Doctors and families are urged to begin therapy earlier and continue it longer than ever before. And an increasing number of young patients, once described in journals as “short normal” children, are now called “short but otherwise healthy”.

It is tremendously satisfying for physicians, as well as enormously profitable for drug manufacturers, to make a child grow. Of course, there is no controversy about providing growth hormone to those youngsters who are truly deficient, and many families are profoundly grateful for medical intervention. However, there are many more incentives to treat than for providing long-term follow up for some 20 or 30 years. Assessing risk versus benefit is complicated enough for an adult, let alone adults who are making decisions on the basis of looking into the presumed future of a young son or daughter. For that matter, how much risk is worth accepting for a healthy child?

The story of treating stature is ultimately the story of temptation. The temptation of parents trying everything to secure their child's current and future happiness or success. The temptation for doctors who want to help children grow and believe that they can alleviate suffering, even of the social variety, with a prescription. The temptations offered by industry, not just in the form of consulting fees but also the more general offer to provide a medical fix for social problems. The temptation to try to see into our children's futures, and for all of us to believe we know more than we do.

As the age of genetic medicine inevitably offers us more cures, who will define what is normal and what is not, who is healthy and who is sick? Will doctors be complicit in reinforcing or increasing stigma, rather than contributing towards the acceptance of wide variation in human beings? Will those of us who are parents and medical consumers urge caution and humility, or give in to pressures to make our children closer to perfect? The history of attempts to modify height is worth considering. The pace of technology will pick up. The temptations are only beginning.