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.
What causes gigantism?
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 the only way to achieve a cure. Your surgeon will gain access to your pituitary gland using the transsphenoidal approach—so named because the route your surgeon takes uses the sphenoid sinus. This natural openings in your body can be used by surgeons to make the surgery less invasive. This bone is located behind your nose, mostly within your skull.
Using precise surgical instruments, your surgeon will enter your nasal cavity and create an opening in your sphenoid bone. At Barrow, our surgeons do not make any external incisions on your face, and you will not have any bruising. Once your surgeon gains access to your sphenoid sinus (the air-filled area behind the sphenoid bone), further openings will be made until a hole is created in the sella turcica—the bone that cradles and protects your pituitary gland.
Once your tumor appears in the operative field, removal of the tumor can proceed. Your surgeon will use high magnification to help distinguish normal pituitary tissue from the tumor.
After the tumor has been removed, your surgeon will clean the tumor cavity and seal it off. At Barrow, our surgeons specialize in endoscopic pituitary surgery. Endoscopic pituitary surgery uses a tiny camera to enter the nostrils to remove the tumor.
The surgery aims to minimize trauma to the tissue surrounding your pituitary gland while facilitating a speedy recovery with as little pain or discomfort as is possible.
Most patients are able to return home the day after their surgery.
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. 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 accurate radiation treatment 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.