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What causes gigantism?

Yesterday, Sandy Allen, the world's tallest woman, passed away at the age of 53. Endocrinologist Daniel Kelley explains how she grew so big
sandy allen, gigantism, pituitary



(AP Photo/Phil Meyers)

Sandy Allen—the world's tallest woman, according to Guinness World Records—died on Wednesday (August 13) in the Indiana nursing home where she lived, the Associated Press reports. Allen was 53 years old and stood seven feet, seven inches (2.3 meters) tall—a full inch taller than Chinese basketball star Yao Ming.

As a child, Allen developed a tumor in her pituitary gland—a pea-size structure at the base of the brain that secretes several hormones that are key to the body's function, including human growth hormone. As a result of the tumor, she developed gigantism—her bones grew excessively, causing, among other things, her prodigious height.

With the large proportions came a host of health issues. Although the cause of Allen's death is unknown, she suffered from diabetes, frequent infections, breathing difficulties and kidney failure. She spent much of her later years confined to a wheelchair.

After a career largely devoted to educating children about accepting others' differences, she returned to Indiana and eventually lived in Heritage House Convalescent Center in her hometown of Shelbyville. It's the very same nursing home where Guinness's oldest living woman, 115-year-old Edna Parker, resides.

ScientificAmerican.com rang up Daniel Kelley, medical director of the Neuro-Endocrine Tumor Center at Saint John's Health Center in Santa Monica, Calif., to find out more about Allen's condition.

Is gigantism a normal consequence of pituitary gland tumors?
I don't know her story at all, but it certainly sounds to me like she was an acromegalic giant. That's the only way it happens--if they had a pituitary tumor. The tumor is making excess growth hormone--it's a growth hormone-secreting adenoma that developed prior to her bone growth stopping, when she was still growing. If someone has excess growth hormone, they become excessively tall and become an acromegalic giant.

How common are these pituitary tumors?
About one in 20 people will have an abnormality in their pituitary gland…. And based on some recent demographic studies, about one in 1,000 people probably have a symptomatic pituitary adenoma [the tumor Allen had]. So, a subset of those--maybe 10 percent would have acromegaly, but it's hard to know.

According to the AP story on her death, Allen said she had her growth surgically stopped in her early 20s. How would doctors do that?
She probably had the tumor removed. The standard treatment for someone who has a pituitary tumor is to remove it through endonasal surgery [in which surgeons go through the nose to cut out the tumor]. The goal is remove all the adenoma to protect the normal pituitary gland.

The other treatment options for someone with acromegaly or gigantism, as she had, is radiotherapy--radiosurgery or stereotactic radiotherapy—that is, giving focused radiation to the pituitary tumor to avoid damage to surrounding structures.

Then the third are medications that block the effects of growth hormone or block the actions of insulin growth factor 1. That's what's called the "second messenger of growth hormone." So, when the growth hormone is released by the pituitary, the liver makes IGF1, and that's how you get the effects of growth hormone--through IGF1.

For people with acromegaly, aside from the gigantism, are there other frequent health defects?
The problem with acromegaly is really quite severe. It's a benign adenoma 99.9 percent of the time, but it can cause health problems including hypertension [high blood pressure], diabetes, obstructive sleep apnea [when breathing stops during sleep], carpal tunnel syndrome [pain, numbness or a tingling sensation in the hand or fingers]. So people with untreated acromegaly gigantism, in addition to the growth problems, they can have premature death because of the other associated problems. They get organomegaly--so all their organs get big, too--so they have a higher incidence of heart disease. Then you couple that with hypertension and diabetes and you can imagine they don't live very long.

How old was she when she died?
Fifty-three.

Is that on the high end?
No. Most people who get a growth hormone secreting adenoma are adults. Children or adolescents that get a growth hormone-secreting tumor develop gigantism, in addition to the other problems associated with the excess growth hormone, because their bones have not stopped growing.

So, if you take your average adult who gets acromegaly--and say he has sleep apnea and hypertension and diabetes, if it's caught early enough, between three and five years, usually the hypertension and diabetes become easier to control. While a lot of the metabolic changes go away, the bony changes don't. What you'll see in someone with acromegaly is they get what's called frontal bossing [an enlarged forehead], prognathism--their jaw juts out--they get spreading of the teeth, they get enlarged hands and feet. Your height doesn't increase, but your shoe size and ring size goes up. Your tongues gets big; that's why you snore a lot and get sleep apnea. And then your organs get big.

How does the pituitary adenoma arise?
Most people with pituitary adenoma have a spontaneous [genetic] mutation. We don't really quite know what triggers them. There are some instances--there's something called multiple endocrine neoplasia, which is associated with familial pituitary tumors. But, that's pretty uncommon.

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