NEW YORK (Reuters Health) - Years ago, tall girls often received hormones to stunt their growth -- and now as adults they seem to have more difficulty becoming pregnant than women who weren't treated, a new Dutch study reveals.

The study is the second to show that stunting girls' growth, which was widely done in Europe, Australia, and the United States starting in the 1950's, may have long-term consequences on their reproductive systems.

The treatment involves high doses of the female hormone estrogen. Purposely stunting the growth of tall girls is less common today, but it's not unheard of.

The message from the findings needs to reach girls who are considering treatment, because the risk of reduced fertility may outweigh the benefit of reduced height, said Dr. Emile Hendriks, the lead author of the study from the Erasmus Medical Center in Rotterdam, The Netherlands in email to Reuters Health. "It also needs to reach treated women who need to be well informed when they consider their family planning."

This use for estrogen gained popularity about 50 years ago after researchers found it might limit the growth of girls who were much taller than their peers in adolescence. According to one estimate, up to 5,000 girls in the U.S. were treated with estrogen, and many more in Europe.

At that time, "women were basically supposed to get married and have children, and that would be harder if you were a very tall woman, everybody believed," Christine Cosgrove, co-author of Normal at Any Cost: Tall Girls, Short Boys, and the Medical Industry's Quest to Manipulate Height, told Reuters Health.

"There were so many parents, mostly mothers probably, who just feared that their daughters' lives would be ruined if they ended up being six feet tall, because they'd never have a husband and a family," she said.

Some tall girls are still treated with estrogen today -- more in Europe than in the United States -- and estrogen is currently given to these girls in about the same dose that is in a birth control pill, Cosgrove said. In the past, it might have been given at 100 times that dose before doctors realized the potential dangers, she said.

For the current study, Hendriks and his colleagues recruited 239 Dutch women who had been treated as adolescents between 1968 and 1998 with high doses of estrogen to stunt their growth. They also gathered another group of tall women who had not been treated. All of the women filled out questionnaires about their attempts to conceive and any fertility treatment they had needed.

Women who had the estrogen treatment were more likely to have trouble conceiving than untreated women, according to results published in the Journal of Clinical Endocrinology & Metabolism.

Of those who had tried to get pregnant after being treated with estrogen, 82 percent successfully conceived, compared to 95 percent of untreated women who conceived.

And 71 percent of the treated women gave birth to a live baby, compared to 90 percent of the untreated group.

It also took women treated with estrogen longer to get pregnant -- 56 percent were able to conceive in less than a year of trying, whereas 79 percent of untreated women got pregnant over that same time span. In addition, estrogen-treated women were more likely to get infertility treatment or to visit a doctor for problems related to infertility.

Some of the women in each group underwent tests to determine how well their ovaries were functioning. It turned out that treated women were almost three times as likely to have ovaries that showed signs they might be about to fail, based on hormone levels. That could be one of the reasons these women had more trouble getting pregnant, according to the authors.

The study is important because it's only the second one of its kind, researchers say, although the finding that high doses of estrogen in adolescence may impact fertility later on isn't necessarily surprising.

In an interview with Reuters Health, Dr. Donna Baird, who heads the Women's Health Group at the National Institute of Environmental Health Sciences and was one of the authors of the first study to show this link, said, "The time when (the ovary) is developing in adolescence is clearly an important time. Anything that a girl is exposed to at that time may have much more effect."

Some boys have also been treated with hormones -- in their case, testosterone -- in attempts to stunt their growth. One study suggested testosterone treatment may not affect boys' fertility in the future but is linked to lower testosterone levels when they become adults (see Reuters Health story of October 27, 2010.)

In the opposite scenario, treating short kids with growth hormone during adolescence to help them grow taller has been gaining in popularity in recent years. Until recently, this treatment was only used when there was a medical reason for short stature. The treatment was only started on kids with no medical basis to their short stature within the last decade, and "we don't have the real long-term data," Dr. Joyce Lee, a pediatric endocrinologist in the University of Michigan Health System who was not involved in the current research, told Reuters Health. "We need to wait 30 years to find that answer."

In another recent study, many doctors said they would keep treating short kids with growth hormone even if they weren't responding after a year on the treatment (see Reuters Health story of August 30, 2010.)

"There's always going to be unknown consequences of any medical therapy," Lee said. "The important lesson is, (estrogen) wasn't really prescribed for life-threatening causes," just as growth hormone treatment isn't generally a life-or-death matter today.

"Being tall or being short isn't a disease in most cases," Cosgrove said. "These efforts to treat it as one I think are probably doomed to backfire, and they seem to be backfiring now."

SOURCE: Journal of Clinical Endocrinology & Metabolism, online February 2, 2011.

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