What is Gigantism?
Gigantism is described as accelerated growth during childhood from the production of excess growth hormone. By definition, gigantism must occur during childhood before the growth plates in the long bones of the body (for example, the femur or humerus) have closed. In adults, the condition is called acromegaly.
Gigantism is most often caused by a benign tumor on the pituitary gland called a pituitary adenoma. However, it can also be caused by the following disorders:
- McCune-Albright syndrome (MAS)
- Carney complex
- Multiple endocrine neoplasia type 1
- Abnormally tall stature
- Abnormal growth of the face, hands and feet
- Thickened facial features
- Irregular menstrual cycle
- Excessive perspiration with slight activity
- Delayed puberty
- Double vision
Surgery is the best form of treatment and cures 80 percent of the cases of gigantism. Your child’s surgeon will gain access to your child’s pituitary gland using the transsphenoidal approach—so named because the route crosses, or transects, the sphenoid bone. This bone is located behind your child’s nose, mostly within their skull.
Using precise surgical instruments, the surgeon will make an incision through your child’s nasal cavity to create an opening in the sphenoid bone. Once the surgeon gains access to your child’s sphenoid sinus (the air-filled area behind the sphenoid bone), further incisions will be made until a hole is created in the sella turcica—the bone that cradles and protects the pituitary gland.
After your child’s pituitary gland is in the operative field, removal of the tumor can proceed. Your child’s surgeon will use high magnification to readily distinguish normal pituitary tissue from the tumor.
Once the tumor has been removed, your child’s surgeon will clean the tumor cavity and seal it.
At Barrow Neurological Institute at Dignity Health St. Joseph’s Hospital and Medical Center, our surgeons specialize in two types of surgery for adenomas:
- Microsurgery uses a powerful operating microscope to help your child’s surgeon distinguish between tiny structures in and around the pituitary gland.
- Endoscopic surgery uses small tubes and a tiny camera to help your child’s surgeon remove the tumor in small pieces.
Most patients are able to return home the day after their surgery for removal of a pituitary adenoma, and nasal packing is seldom required.
Pharmacological Treatment and Hormone Therapy
Treatment with a prescription medication is possible if surgery does not cure your child’s gigantism or if surgery is not recommended. Medicines are also sometimes prescribed before surgery to improve the likelihood of a good outcome.
- Octreotide or lanreotide are synthetic forms of the hormone somatostatin and stop the release of growth hormone. They are often effective for the long-term control of gigantism, but they can only be administered by injection every two to four weeks. If your child’s tumor is particularly large, these drugs may be administered before surgery. Due to the side effects of these drugs and their expense, surgery to achieve a long-term cure is preferable.
- Bromocriptine and cabergoline are from a class of drugs called dopamine agonists. They can lower IGF-1 and growth hormone levels in about half of the people treated with them (although your symptoms could improve even if your IGF-1 and growth hormone levels do not decrease). Although not as effective as the synthetic hormones octreotide and lanreotide, they are less expensive and more convenient to administer, because no injection is required. They can be combined with octreotide in children with no adverse effects on long-term health.
- Pegvisomant is a recently developed drug that blocks the action of growth hormone in your body, thereby lowering IGF-1 levels. It must be administered by subcutaneous (beneath the skin) injection daily. It is another option if your child does not respond to surgery or other medications, or if your child cannot tolerate these treatments for other reasons.
Gamma Knife radiosurgery is a highly advanced form of radiotherapy that is used to achieve similar results to the traditional surgical techniques described above. However, with Gamma Knife it can take several years for growth hormone and levels to return to normal, rather than days or weeks as with traditional surgery. It is typically a treatment of last resort in patients with gigantism.
The ‘knife’ in this surgery is actually made up of many small beams of radiation focused on a single point. Each individual beam too weak enough to damage healthy tissue, but at the point where the beams converge they deliver a dose of radiation that is lethal to the tumor.
Gamma Knife is an outpatient procedure, does not involve any incisions, and requires only brief sedation under general anesthetic.
However, there are additional considerations for pediatric Gamma Knife surgery. These are best discussed with your child’s neurosurgeon.
How common is gigantism?
Gigantism is an extremely rare condition that only occurs in children. About 100 cases have been reported in the United States. Gigantism has been reported to occur at a female-to-male ratio of 1:2.
How is gigantism diagnosed?
Magnetic resonance imaging (MRI) is used to determine the size and location of your child’s tumor if it is suspected that the disease is caused by a pituitary adenoma.
Furthermore, several blood tests can provide a diagnosis. High levels of prolactin or increased amounts of insulin growth factor-1 (IGF-1) can suggest acromegaly, as can high levels of growth hormone in the blood after oral administration of a large dose of glucose. Low levels of cortisol, thyroid hormone, testosterone (in boys), and estradiol (in girls) can also suggest involvement of the pituitary gland.