What is gigantism?

Causes and Symptoms

Gigantism is a rare disease
most often caused by the presence of tumors
of the peanut-sized pituitary gland
, located at the base of the brain. Such tumors produce an excess of growth hormone, the biomolecule responsible for overall growth. In children or adolescents who have these tumors, excess growth hormone results in overgrowth of all parts of the body. Gigantism occurs because the bones of the arms and legs have not yet calcified and can grow much longer than usual. Hence, an afflicted child becomes very large in size and very tall, often reaching a height of more than 6 feet, 6 inches.

A young child afflicted with pituitary gigantism grows in height as much as six inches per year. Thus, an important symptom that identifies the problem is that such children are much taller and larger than others of the same age. In many cases, this great size difference may lead to individuals who are more than twice the height of their playmates. Excessive growth of this sort should lead parents to seek the immediate advice of their family physician, who can aid in the selection of a specialist to identify the problem and develop an appropriate treatment.

As gigantism proceeds, pituitary tumors often invade and replace the rest of the pituitary gland. This is unfortunate, because the pituitary gland produces several other hormones
—called "trophic hormones"—that control mental processes, sexual maturation, and healthy overall growth. Consequently, prolonged, untreated gigantism may yield a huge individual who suffers from mental illness, is sexually immature, and becomes quite unhealthy. In addition, the human musculoskeletal system is not designed to accommodate individuals attaining the great heights of many postadolescent pituitary giants. Hence, it is fairly common that affected individuals have great difficulty standing and walking; some can do so only with the aid of canes. Moreover, the average life expectancy of an individual with untreated gigantism or acromegaly is shorter than that of individuals of normal stature.

In cases where pituitary tumors that oversecrete growth hormone occur after calcification of the long bones is complete—after adolescence—gigantism will not occur. Such individuals develop acromegaly. This often-fatal disease, progressive throughout life, thickens bones and causes the overgrowth of all body organs. Hands and feet grow larger, and the lower jaw, brow ridges, nose, and ears enlarge, coarsening the features. More damaging is the development of headaches, high blood pressure, high cholesterol levels, arthritis, type 2 diabetes, sleep
apnea, and even colon
cancer over the long run. It should be noted that these disabilities are rarely seen in pediatric patients and most often begin in the third or fourth decade of life. Many medical scientists believe that pituitary gigantism and acromegaly are the basis for the legends about giants and ogres.

Treatment and Therapy

If a diagnosis of gigantism or acromegaly seems probable, the physician or specialist involved will order a blood test to identify the amount of growth hormone present in the body. Computed tomography (CT) and magnetic resonance imaging (MRI) scans will also be carried out, especially in those suspected of having acromegaly, to identify possible organ changes away from normal size.

In cases where growth hormone levels are high and cannot be reduced by chemotherapy—for example, with antigrowth hormone drugs such as somatostatin analogs, dopamine agonists, and growth hormone receptor antagonists—and/or the presence of a clearly defined tumor is identified via CT and MRI, surgery to excise the tumor will be attempted. Radiation therapy is associated with a number of detrimental effects and with a slower response time; thus, chemotherapeutic and surgical interventions are preferred over radiation in most cases.

Perspective and Prospects

It must be recognized that the success of any therapeutic regimens or their combination will prevent additional gigantism or symptoms of acromegaly from occurring. It is not possible, however, to reverse existing consequences of the pituitary tumors on young children and adolescents with gigantism or on adults with acromegaly.

For this reason, it is essential for worried parents or adult patients to visit an appropriate physician as quickly as possible. Such foresight will usually minimize problems associated with either manifestation of pituitary tumors and enable an afflicted individual to have the best possible future life. In addition to extirpating causative tumors, it will then become possible, after additional blood tests and the thorough examination of CT and MRI data, to identify which body organs need to be treated and to arrest or minimize health complications, such as those associated with the reproductive, cardiovascular, and musculoskeletal systems.

Bibliography

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