Gigantism and acromegaly occur when the pituitary gland produces too much growth hormone. The pituitary gland is a small structure that’s found at the base of the skull. It produces growth hormone, which helps the body grow during puberty.
Gigantism and acromegaly are similar, but they also have notable differences.
For starters, gigantism occurs in children. The overproduction of growth hormone occurs during puberty, when a child is still naturally growing. This causes increased height and size for the child’s age.
Gigantism is extremely rare. Barrow Neurological Institute estimates there have been just 100 cases in the United States.
On the other hand, acromegaly affects middle-aged adults. It’s caused by an overproduction of growth hormone, even after puberty. This causes atypical growth in adulthood.
Acromegaly is rare and progresses slowly. The National Organization for Rare Disorders says it’s more common than gigantism, affecting about 50 to 70 people out of 1 million.
The following chart compares gigantism and acromegaly:
| Gigantism | Acromegaly | |
|---|---|---|
| Age of onset | childhood, before puberty | adulthood, after puberty |
| Cause | pituitary and nonpituitary tumors | pituitary tumors or conditions like McCune-Albright syndrome, Carney complex, or GPR101 gene mutation |
| Main symptoms | tall height, large size, enlarged extremities and facial features | enlarged extremities and facial features |
| Onset of puberty | delayed | typical |
| Progress of symptoms | rapid | slow |
| Diagnosis | physical exam, imaging tests, blood tests | physical exam, imaging tests, blood tests |
| Preferred treatment | surgical removal of tumor | surgical removal of tumor |
Although gigantism and acromegaly are both caused by excess growth hormone, they have different symptoms. This is due to the age at which each condition develops.
Symptoms of gigantism
A child with gigantism will be much larger and taller than other children of the same age. Other symptoms include:
- large hands and feet
- thick toes and fingers
- very soft hands
- enlarged jaw and forehead
- significant underbite
- enlarged tongue, nose, and lips
- deepening voice in boys
- oily skin
- excessive sweating
- skin tags
- joint pain
- headache
- difficulty sleeping
- irregular menstrual periods
Symptoms of acromegaly
Since acromegaly develops slowly, the symptoms can be easy to miss. The symptoms can also vary widely.
Possible symptoms include:
- enlarged hands and feet
- misalignment of teeth
- enlarged lips, tongue, or jaw
- deeper voice
- muscle weakness
- inability to sleep
- fatigue
- headaches
- joint inflammation and pain, especially in large joints
- curved spine
- thickened or darkened skin
- oily skin
- excessive sweating
- difficulty breathing
- irregular heartbeat
- excessive body hair
- skin tags
- spaces between the teeth
- splayed fingers and toes
- vision difficulties
Gigantism and acromegaly are primarily caused by excess growth hormone. Most commonly, these conditions are caused by a benign, or noncancerous, tumor in the pituitary gland. The tumor is called a pituitary adenoma.
Not all pituitary adenomas produce excess growth hormone. But if they do, it can cause gigantism or acromegaly, depending on a person’s age.
Other gigantism causes
In some cases, gigantism might be related to other conditions, like:
- Carney complex
- McCune-Albright syndrome
- multiple endocrine neoplasia type 1 or 4
- neurofibromatosis
- GPR101 gene mutation
Other acromegaly causes
Rarely, a tumor somewhere else in the body can cause acromegaly. This includes tumors in the:
- lungs
- pancreas
- hypothalamus
- adrenal glands
- chest or abdomen
These tumors typically secrete hormones that trigger the pituitary gland to make growth hormones. Sometimes, these tumors might produce growth hormone themselves.
Gigantism does not turn into acromegaly. That’s because each disorder is defined by the age when it begins.
If a person overproduces growth hormones during childhood, they’ll have gigantism. As an adult, they will still have gigantism, because their condition developed when they were a child.
Gigantism will not turn into acromegaly, because acromegaly is a condition that specifically develops in adulthood.
Due to the excess growth hormone, both gigantism and acromegaly can cause various risks and complications.
Complications of gigantism
Gigantism may lead to:
- high blood pressure
- diabetes
- heart disease
- heart failure due to an enlarged heart
- thyroid cancer
- hypothyroidism
- colon polyps
- hypopituitarism, or the low secretion of pituitary hormones
- delayed puberty
Complications of acromegaly
The complications of acromegaly are similar to those of gigantism. The condition may increase your risk of:
- high blood pressure
- diabetes
- sleep apnea
- heart disease
- hypopituitarism
- arthritis
- uterine fibroids
- colon polyps
- vision issues
- compressed spinal cord
The following images show individuals with gigantism and acromegaly.
Diagnosing gigantism and acromegaly involves similar tests:
- Medical history. Your doctor will want to learn more about your family history and current symptoms. This information can help them determine if you need additional tests.
- Physical examination. This allows your doctor to look for physical symptoms, like an enlarged tongue or prominent facial bones.
- Blood tests. Gigantism and acromegaly involve high blood levels of growth hormone and insulin growth factor-1 (IGF-1). Your doctor might also check other hormones, like cortisol and thyroid hormone, which may be low.
- Imaging tests. If your doctor thinks a pituitary adenoma is causing your symptoms, they may order an MRI or CT scan. This test will show the size and location of the tumor.
In both conditions, the goal of treatment is to lower the body’s production of growth hormones. This will likely include a combination of the following several therapies.
Surgery
If gigantism or acromegaly is due to a tumor, the preferred treatment will be surgery to remove it.
During surgery, a neurosurgeon will insert a camera into your nose. They’ll remove all or part of the tumor, which will help lower the production of growth hormone.
This option is ideal as long as the tumor is in an accessible location. If the tumor is hard to reach, or if it’s too large, your doctor might not recommend surgery.
Medication
Medication can help lower growth hormone levels. It may be used in the following scenarios:
- Growth hormones are still high after surgery.
- You’re unable to get surgery.
- Your doctor wants to try and shrink a large tumor before surgery.
The following types of medication can help regulate growth hormone production:
- somatostatin analog
- dopamine agonists
- growth hormone receptor antagonists
Radiation therapy
If surgery is ineffective or not an option, your doctor might recommend radiation therapy. It destroys tumor cells using a beam of radiation. This can help shrink the tumor and lower growth hormone levels.
Options include:
- Stereotactic irradiation. Stereotactic irradiation may be used for gigantism or acromegaly. It applies one high dose of radiation to the tumor. This won’t destroy the surrounding tissues, but it can take about 18 months to lower growth hormone levels.
- External irradiation. This option is typically used for acromegaly. It involves smaller doses of radiation, which you’ll receive over several years every 4 to 6 weeks.
A side effect of radiation is hypopituitarism, or low pituitary hormone production. That’s because the radiation destroys part of the pituitary gland.
If you have gigantism or acromegaly, it’s important to visit your doctor regularly. They can help manage your growth hormone levels by providing the most appropriate treatments.
If you’ve had surgery, your growth hormone levels will be measured after 12 weeks. Surgery can successfully treat up 50 to 80 percent of cases, according to the UCLA Pituitary and Skull Base Tumor Program, depending on the size of your tumor. The success rate is higher for smaller tumors.
You may also need regular testing to manage complications. This includes tests like:
Regardless of your treatment plan, your doctor will continue to monitor your growth hormone levels and pituitary gland function.
Gigantism and acromegaly are both caused by excess growth hormone. Gigantism, which develops during childhood, may be caused by a pituitary tumor or underlying condition. Acromegaly appears in adulthood and is often caused by a tumor in the pituitary gland.
To diagnose either condition, a doctor will use a physical exam, imaging tests, and blood tests. The preferred treatment is surgical removal of the tumor, but medication and radiation therapy may also be used.
The goal of treatment is to manage growth hormone levels. Your doctor can determine the best treatment plan for your situation.