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They might be giants: what makes the Washington Bullets' Gheoghe Muresan so tall?

The Washington Bullets may not have a chance of taking the National Basketball Association championship this June, but the team does have one record clinched: At an incredible 2.3 meters (7ft, 7in.), the Bullets' center--Gheorghe Muresan--is the tallest player in the NBA.

How did Muresan get so tall? Could you end up towering over your friends too? Read on and find out!

GROWING PAINS

Muresan started growing rapidly when he was just 6 years old. He shot up abnormally fast because he has a disorder of the endocrine system--a network of glands (organs) that work together to produce chemicals called hormones. Hormones, which travel in your bloodstream to specific organs or tissues, control an amazing range of activities in your body--everything from how hungry you feel to how fast you grow.

"On average, kids grow about two and a half inches a year,' explains Dr. Alan Rogol, a pediatrician at the University of Virginia. That happens when your hypothalamus--a combination of nerve and gland tissue in your brain--sends a signal to two glands: your pituitary gland and your thyroid gland (see diagram, p. 11). In response, the pituitary produces a chemical called growth hormone and the thyroid makes a hormone called thyroxine. Together, thyroxine and growth hormone instruct cells on the ends of your arm and leg bones to divide. As the cells divide, your bones grow longer and you get taller.

When Muresan was growing up, his pituitary gland probably pumped out 10 to 100 times the normal amount of growth hormone. That's because he has a tumor (abnormal tissue growth) on his pituitary, which made the gland work overtime.

Usually, the amount of hormone an endocrine gland produces is controlled by a feedback mechanism--the body's on/off switch, tissue, like bone, responds to a hormone, the tissue signals the gland to stop or slow hormone production. When the level of the hormone in the bloodstream drops too low, the tissue signals the gland to restart or increase output.

Muresan's bones sent out signals to stop his growth-hormone production, but the tumor in his pituitary gland didn't respond--and he kept growing. By the time he was 10 years old, he was already taller than everyone else in his family. And he still had a growth spurt ahead of him.

GIANT STEPS

A growth spurt--which usually lasts 12 to 24 months--is a period during which an average kid sprouts up to 10 to 15 centimeters (4 to 6 in.) each year. This speeded up growth rate occurs during puberty--a time when your endocrine system markedly increases its production of the hormones testosterone and estrogen. These hormones signal the pituitary gland to start pumping out two to three times as much growth hormone as it did before puberty.

Girls usually begin their growth spurts when they are between 11 1/2 and 12 1/2 years old, Dr. Rogol says. Most boys start about two years later. Why the big difference? Nobody knows! "The hypothalamus signals the start of puberty," explains Dr. Eric Smith, a pediatrician at Cincinnati's Children's Hospital, "but how it does that isn't understood very well."

One thing is certain: Muresan had a giant growth spurt. By the time he was 14, he stood over 2 meters (6ft, 9in.) tall. And he kept on growing--another 25 centimeters (10in.) before his growth spurt ended! The medical term for growing extremely tall due to an overproduction of growth hormone is gigantism. Not more than one in a million children has this disorder, says Dr. Smith. Doctors could have treated Muresan's gigantism by removing his tumor, but he grew up in a small village in Romania where treatment wasn't available.

Even without treatment, Muresan's growth spurt ended when the hormone estrogen signalled the cells at the end of his leg and arm bones to stop dividing. After this message is sent, humans can't grow any taller no matter how much growth hormone they produce.

A few years ago, doctors removed most of the tumor in Muresan's pituitary gland. But because a small part of the tumor couldn't be removed, Muresan still produces too much growth hormone. Since his bones can't get any longer, the extra growth hormone is mixing the bones of his hands, feet, jaws, and the skin on his forehead and feet thicken. This extremely rare adult disorder is called acromegaly.

Another endocrine disorder, called pituitary dwarfism, most frequently occurs when a child's hypothalamus never sends a growth-hormone-releasing signal to the pituitary. If untreated, adults with this disorder are unusually short--sometimes standing just 120 centimeters (4ft) tall. This condition can be treated with injections of growth hormone, which allow kids to grow to a normal height. (Many other causes of dwarfism exist, and most aren't easily treated.

GROW WITH THE FLOW

Endocrine disorders like these are very rare, says Dr. Smith, but kids who worry about their growth seem to be everywhere. One reason some kids stress out about their height is the wide range of what's considered "normal" growth, Dr. Smith says. For example, some girls enter puberty--and really start to grow-when they're 8 years old. Other girls are almost 13 before they hit their growth spurt. And boys can start even later--sometimes at age 16.

"That creates some tension,' Dr. Smith says. Questions come up as to why I'm different from the person sitting next to me in class. " But even teens who start their growth spurts late--most often because their Parents were also "late bloomers"--usually end up reaching their adult height by the time they graduate from high school.

"Be patient about growing," suggests Dr. Smith. "The most important thing you can do is tolerate people's natural differences--including your own." After all, "short" people make the record books too. Just ask the Charlotte Hornets' point guard Muggsy Bogues. At 1.6 meters (5ft, 3in.), he's the shortest player in the NBA. Even though Bogues is 70 centimeters (2ft, 4in.) shorter than Muresan, he scored almost six points more per game last season than the tall man!

* The pea-size pituitary gland in your brain controls growth and other bodily functions by releasing just a millionth of a gram of homones into your body daily.

* A hormone may travel through your entire body in your bloodstream before reaching the target tissue where it makes chemical changes.

* Your bvody produces growth hormone in bursts--with the greatest amount produced during deep sleep. Lack of sleep may in reduced production of the hormone

RELATED ARTICLE: ESTIMATE YOUR FUTURE HEIGHT

This graph shows the broad range of "normal" growth. To get and idea of your likely adult height, calculate one of the equations below.

For girls: Add your father's height and your mother's height (in centimeters). Subtract 13cm and divide by two. The answer is your adult height plus or minus 10cm.

For boys: Add your father's height and your mothers's height (in centimeters). Add 13cm and divide by two. The answer is your adult height plus or minus 10cm.

[ILLUSTRATION OMITTED]

DEBATE

Should kids who want to be taller get injections of growth hormone?

Scientists have developed a synthetic (artificial) growth hormone to help kids who lack natural growth hormone get taller. now some people--mostly parents--want healthy kids who are short to get the injections too. Do you think that's a good idea? Here's what people on both sides of the debate say.

PRO:

* Kids who are short--especially boys--get teased about their height.

* Some doctors feel that growth-hormone injections may encourage development in "late bloomers," allowing them to catch up with their classmates.

* Society often views taller people as being more confident, attractive, and physically stronger.

* Short people sometimes have trouble finding clothes that fit or reaching objects overhead.

CON:

* Low doses of growth hormone may not make healthy, short kids grow taller.

* High doses may have serious side effects--including heart disease.

* Injections are expensive: about $20,000 a year.

* Given time, most kids will grow taller naturally.

* There's nothing wrong with being short.

Do you think growth hormone should be available to short kids who want to be taller? Check out what some other Science World readers say, then debate and decide.

YES "If a kid wants the injections and her parents say it's all right, she should be allowed to have them. But I think it's better to be happy with who you are."

Mary Jo Kidd, 13

Eula Junior High

Clyde, TX

NO "Growth hormone could have side effects we don't even know about. It's better just to wait and see if you grow naturally."

Matt Robertson, 13

Ramer Elementary

Ramer, TN

"Taking growth-hormone injections sounds a lot like taking steroids--which have serious side effects. Growth hormone would probably have side effects too."

Latoya Laws, 12

Goudy School

Chicago, IL

"Diversity is important. Tall people are good at some things and short people are good at others."

Mark kicsak, 18

Whitney Point High School

Whitney Point, NY
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Copyright 1996, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
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Title Annotation:over-production of growth hormone
Author:Costello, Emily
Publication:Science World
Date:Feb 23, 1996
Words:1481
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