Gigantism is abnormally large growth due to an excess of growth hormone during childhood, before the bone growth plates have closed.
Causes, incidence, and risk factors
The most common cause of too much growth hormone release is a noncancerous (benign) tumor of the pituitary gland. Other causes include:
- Carney complex
- McCune-Albright syndrome (MAS)
- Multiple endocrine neoplasia type 1 (MEN-1)
If excess growth hormone occurs after normal bone growth has stopped, the condition is known as acromegaly.
Gigantism is very rare.
The child will grow in height, as well as in the muscles and organs. This excessive growth makes the child extremely large for his or her age.
Other symptoms include:
Signs and tests
- CT or MRI scan of the head showing pituitary tumor
- Failure to suppress serum growth hormone (GH) levels after an oral glucose challenge (maximum 75g)
- High prolactin levels
- Increased insulin growth factor-I (IGF-I) levels
Damage to the pituitary may lead to low levels of other hormones, including:
In pituitary tumors with well-defined borders, surgery is the treatment of choice and can cure many cases.
For situations in which surgery cannot completely remove the tumor, medication is the treatment of choice. The most effective medications are somatostatin analogs (such as octreotide or long-acting lanreotide), which reduce growth hormone release.
Dopamine agonists (bromocriptine mesylate, cabergoline) have also been used to reduce growth hormone release, but these are generally less effective. Pegvisomant, a medication that blocks the effect of growth hormone, may be used.
Radiation therapy has also been used to bring growth hormone levels to normal. However, it can take 5 - 10 years for the full effects to be seen and almost always leads to low levels of other pituitary hormones.
Radiation has also been linked to learning disabilities, obesity, and emotional changes in children. Most experts will use radiation only if surgery and medication fail.
Pituitary surgery is usually successful in limiting growth hormone production.
- Delayed puberty
Surgery and radiation can both lead to low levels of other pituitary hormones, which can cause:
Calling your health care provider
Call your health care provider if your child has signs of excessive growth.
Melmed S, Kleinberg D. Anterior pituitary. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR. Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008:chap 8.
Reviewed By: Ari S. Eckman, MD, Division of Endocrinology and Metabolism, Johns Hopkins School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.