Gigantism: Symptoms, Causes, Diagnosis, Treatment


Growth hormone is a key hormone, produced by the pituitary gland that regulates growth during childhood by directly promoting bone growth and helping to control metabolism. It is a relatively stable process during childhood through puberty.

During puberty, the secretion of sex hormones (estrogen in girls and testosterone in boys) increases significantly and causes the growth plates (epiphyses) at the ends of long bones to slowly fuse. Growth in height stops at the end of puberty when the growth plates have fully fused.

Gigantism is a rare endocrine disorder caused by very high levels of growth hormone, which is found during childhood and adolescence before the growth plates in the bones close.

Excessive amounts of growth hormone accelerate the growth of muscle, bone, and connective tissue leading to an abnormal increase in height, as well as a number of additional soft tissue changes. When left untreated or uncontrolled, some individuals with gigantism can grow to more than 2.43 meters. The most famous example is Robert Wadlow, the tallest person in history at 2.71 meters, citing the Society for Endocrinology website .

1. The difference between gigantism and acromegaly
Gigantism and acromegaly are conditions that result from excess growth hormone (GH). The difference lies in who is affected—acromegaly develops in adults, whereas gigantism affects children and adolescents who are still growing.

Gigantism is less common than acromegaly, as reported by the Cleveland Clinic.

2. Symptoms
Explained on the MedlinePlus site , the child’s height will increase, as well as his muscles and organs. This excessive growth makes the child very large for his age.

Other symptoms include:

Delayed puberty.
Double vision or difficulty with peripheral vision.
A very prominent forehead ( frontal bossing ) and a protruding jaw.
Gaps between teeth.
Increased sweating.
Irregular menstruation (menstruation).
Joint pain.

Express breast milk.
Thickening of facial features.
Voice change.

3. Cause
The most common cause of gigantism is a benign (noncancerous) tumor of the child’s pituitary gland (pituitary adenoma) that releases excessive GH. Children with gigantism almost always have a large pituitary tumor called a macroadenoma (a pituitary adenoma that is 10 millimeters in diameter or larger) at diagnosis. Gigantism can also be caused by pituitary hyperplasia, which is when the pituitary gland enlarges.

Many children with gigantism have a genetic mutation that causes a pituitary tumor to form. The most common genetic mutation associated with gigantism is a mutation or deletion of the AIP gene, which makes up about 29 percent of the population of people with gigantism.

Gigantism can occur as part of several rare genetic disorders that lead to an increased risk of developing GH-secreting pituitary tumors. This includes:

Carney complex: This is a genetic condition that affects skin color (pigmentation) and causes benign tumors of the skin, heart, and endocrine system. GH-secreting pituitary adenomas occur in about 10 percent to 13 percent of Carney complex cases and are usually slow-growing.
McCune-Albright syndrome: This is a genetic condition that affects the bones, skin, and endocrine system, causing café-au-lait skin pigmentation (a light to dark brown pigmented birthmark that usually appears on the skin of newborns), the formation of scar tissue on the bones , and early puberty. Excess GH is present in 20 percent to 30 percent of cases of McCune-Albright syndrome. It is often caused by enlargement of the pituitary gland (hyperplasia), but pituitary adenomas can also cause it.
Multiple endocrine neoplasias (MEN) type 1 or type 4: This is a genetic condition when one or more endocrine glands are overactive and/or form tumors, which can include GH-secreting pituitary tumors.
Neurofibromatosis: This is a condition that is part of a group of genetic conditions known as neurocutaneous disorders that affect the skin and nervous system. This type of disorder is caused by an abnormal increase in cell growth. This results in the formation of tumors throughout the body, which can include GH-secreting tumors.
Familial isolated pituitary adenomas (FIPA): This is an inherited condition characterized by the development of pituitary adenomas, which can include GH-secreting adenomas.
Gigantism is a very rare condition. The main risk of this condition is having a parent or sibling with gigantism.

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4. Diagnosis
A doctor who sees a child growing unusually fast will need to ask several questions and perform a physical examination, which may include checking height, weight, body proportions, senses, and stage of puberty.

Described on the Healthdirect page , tests to diagnose gigantism include:

Blood tests: To measure levels of hormones and sometimes other substances.
Oral glucose tolerance test: To see how growth hormone levels change when blood sugar levels rise.
MRI or CT scan: To view the pituitary gland.
X-rays of the skull and jaw: To check the thickness of the bones.

5. Treatment
The goals of gigantism treatment include:

Safely controls levels of GH and insulin-like growth factor 1 (IGF1).
Controls the growth of pituitary tumors.
Reduces the effect of pituitary tumors on nearby structures, such as brain tissue and the optic nerve.
Treats or reduces the effects of GH on other body systems.
Doctors usually use a combination of treatments, particularly surgery and radiation therapy, for gigantism.

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Medications are available and effective in treating acromegaly (excess GH in adults) but the effects of these drugs in children have not been adequately studied.