Gigantism vs. acromegaly: What is the difference?

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The following chart shows a comparison of gigantism and acromegaly:

Excess growth hormone causes both gigantism and acromegaly.

The main difference between the two is that gigantism occurs in children before puberty, and acromegaly happens after puberty during adulthood. Acromegaly occurs most often between ages 30 and 50.

Because these conditions arise during different stages of growth, they have slightly different symptoms.

Symptoms of gigantism occur rapidly. Children become much taller than others of the same age.

The changes induced by acromegaly occur slowly, so it can be many years after symptoms start before someone receives a diagnosis.

Acromegaly is rare, affecting approximately 50–70 people out of 1 million. Gigantism is very rare, with about 100 reported cases in the United States.

Learn more about acromegaly.

Because of the ages at which gigantism and acromegaly develop, they have different symptoms.

Gigantism

With gigantism, excessive growth hormone production starts before the bone growth plates close. The growth plate is the area near the ends of a child’s long bones from which bone growth occurs.

Each long bone has a growth plate at each end that closes with solid bone replacing it once a child has finished growing.

Excess growth hormone causes long bones to grow significantly, resulting in children becoming taller and larger than children of the same age.

Symptoms of gigantism may include:

• excessive growth in height, muscles, and organs
• enlarged hands and feet with thick fingers and toes
• thickening of facial features
• prominent forehead and jaw
• delayed puberty
• irregular menstrual periods
• difficulty with side vision or double vision
• increased sweating
• weakness

Acromegaly

Acromegaly occurs in adulthood after normal bone growth is complete, so increased growth hormone cannot increase bone length. However, it can deform bones rather than elongate them.

Symptoms of acromegaly may include:

• enlarged hands and feet
• thickening of facial features
• protruding lower jaw
• misalignment between teeth
• unusually thick lips and a large tongue
• joint and muscle pain
• osteoarthritis
• enlarged sinuses and thickened vocal cords that result in a deep, husky voice
• abnormal spine curvature
• trapped nerves due to the overgrowth of tissue
• dark, thicker patches of skin in certain body areas
• excess body hair

Excess growth hormone causes gigantism and acromegaly. Most commonly, an increase in growth hormone occurs due to a pituitary gland tumor called a pituitary adenoma. Pituitary tumors are usually noncancerous.

Not all pituitary adenomas secrete growth hormone, but those that do can cause gigantism or acromegaly, depending on the age of the person.

Gigantism

Sometimes, gigantism links with other conditions, such as:

• Carney complex
• McCune-Albright syndrome
• multiple endocrine neoplasia type 1 or type 4
• neurofibromatosis
• GPR101 gene mutation

Acromegaly

Rarely, acromegaly can happen due to other reasons than a pituitary adenoma.

For example, tumors in the lungs, adrenal glands, and pancreas may cause acromegaly. They could either directly produce increased growth hormone or growth hormone-releasing hormone that stimulates the pituitary gland to secrete growth hormone.

Acromegaly may also occur if the area of the brain called the hypothalamus controls growth hormone-secreting cells ineffectively. Excess amounts of growth hormones can also sometimes result from the hypothalamus or other tissues producing too much growth hormone-releasing hormone.

Genetic syndromes may also contribute to acromegaly, including:

• multiple endocrine neoplasia type 1
• familial isolated pituitary adenoma
• Carney complex
• McCune-Albright syndrome

Doctors diagnose gigantism and acromegaly using similar tests. They first ask about a person’s medical history and conduct a physical examination. They may then order the following tests:

• IGF-1 test: A person must fast overnight for an IGF-1 test. A healthcare professional then takes a blood sample to check the levels of IGF-1 in the blood. Levels of IGF-1 typically parallel those of growth hormone. High levels of IGF-1 suggest a person may have gigantism or acromegaly.
• Oral glucose tolerance test: A doctor orders this test to confirm a diagnosis. A person drinks a sugary liquid, and then a healthcare professional tests their blood every 30 minutes for 2 hours to measure growth hormone levels. Typically, the sugar in the drink causes growth hormone levels to decrease. However, if the levels do not go down substantially, it confirms a diagnosis of gigantism or acromegaly.
• MRI scan: Healthcare professionals use MRI scans to locate the tumor on the pituitary gland and determine its size. If they cannot find a tumor, they order other imaging tests to identify nonpituitary tumors that may be elevating growth hormone levels.

For children with gigantism, a doctor may order additional tests to check the condition is not affecting other parts of their body. These tests may include:

• echocardiogram
• sleep study
• X-rays

Treatment goals for gigantism and acromegaly include:

• controlling the size of the tumor
• regulating growth hormone and IGF-1 levels
• improving symptoms
• treating the effects of growth hormones on other body systems

A doctor will develop an individual plan of treatment that considers factors such as a person’s age, tumor size, symptom severity, and growth hormone and IGF-1 levels. A doctor may recommend:

Surgery

Transsphenoidal surgery can remove pituitary tumors. Transsphenoidal surgery is a method that surgeons use to enter the nose to remove a pituitary tumor.

If the tumor causing elevated growth hormone levels is not on the pituitary gland, surgeons use other types of surgery.

Removing the tumor lowers growth hormone levels and improves symptoms.

Medications

A doctor may recommend one medication or combination of drugs to help normalize growth hormones. These may include the following:

• Somatostatin analogs (SSAs): These drugs signal the pituitary gland to produce less growth hormone. They may also decrease the pituitary tumor size.
• Dopamine-receptor agonists: These medications also curb growth hormone secretion but do not work as well as SSAs.
• Growth hormone-receptor antagonists: This medication helps reduce IGF-1 levels and alleviates symptoms but does not reduce the tumor size or growth hormone levels.

Radiation therapy

Doctors may recommend radiation therapy if surgery is not possible or when surgery cannot remove all the tumor tissue. Radiation therapy uses high energy X-rays to kill tumor cells and slowly lowers growth hormone levels.

Radiation therapy reduces growth hormone and IGF-1 levels over an extended period, so it can take many years for it to have an effect on symptoms.

Gigantism and acromegaly are disorders that result from excessive growth hormone production. Although both conditions are rare, gigantism occurs very rarely.

Gigantism occurs in children before puberty, causing them to be very tall and large. Acromegaly happens during adulthood, causing enlarged hands, feet, and facial features. Both conditions can cause complications to various body systems.

Excessive growth hormone is usually the result of a noncancerous tumor on the pituitary gland. Rarely, it can happen due to tumors in other parts of the body or because of specific genetic syndromes.

Doctors diagnose gigantism and acromegaly with blood and imaging tests. They treat the conditions by removing the tumor and reducing growth hormone levels with surgery, medications, and radiation therapy.