Gigantism classification

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview[edit | edit source]

Classification[edit | edit source]

As a medical term, gigantism can refer to:

Pituitary Gigantism[edit | edit source]

Pituitary gigantism occurs in people who have an over-production of hormones which is due to prepubertal growth hormone excess. This is sometimes equated with acromegaly, but more precisely, an excess of growth hormone leads to "pituitary gigantism" (vertical growth) if the epiphyseal plates have not yet closed,^[1] but it leads to "acromegaly" (lateral growth) if they have closed.

Pituitary growth hormone excess is the single condition that accounts for nearly all cases of pathologic extreme height. The excess growth hormone usually results from oversecretion by a group of somatotrope cells of the anterior pituitary gland (termed a "somatotrope adenoma"). These cells do not respond to normal controls of growth or function. They grow very slowly, so that for many years the only effects of such an adenoma are the secretion of excessive growth hormone. Over decades, such an adenoma may reach a large enough size (20 mm or more in diameter) to cause headaches, impair vision, or damage other pituitary functions. Many years of growth hormone excess can cause other problems as well.

The primary effect of growth hormone excess in childhood is excessive growth, but the extreme height is accompanied by a characteristic physique recognizable to an endocrinologist. The typical physique involves heavy, thick bones, with large hands and feet and a heavy jaw. Once puberty is complete and adult height is achieved, continued thickening of the skin and growth of the jaw results in a combination of features referred to as acromegaly.

If a physician suspects pituitary gigantism or acromegaly, the simplest diagnostic screening test is measurement of insulin-like growth factor 1 in the blood. This is usually quite elevated but levels must be interpreted in relation to age and pubertal status. Additional confirmatory testing may include magnetic resonance imaging (MRI) of the pituitary to look for a visible adenoma, and suppressibility of growth hormone levels by glucose. Treatment depends on the size of the adenoma and may involve removal by a neurosurgeon, drugs such as octreotide or bromocriptine, or radiation. Treatment is discussed in more detail in the acromegaly article.

Childhood pituitary gigantism is a rare condition, and those affected are often unusual enough to attain a degree of celebrity status (for example, André the Giant and The Great Khali). Acromegaly is the term used for the condition of growth hormone excess when it occurs in adults. Acromegaly is a far more common disease in adults than pituitary gigantism is in children.

Cerebral Gigantism[edit | edit source]

"Cerebral gigantism", also known as Sotos syndrome,^[2] which is due to a mutation in NSD1.

References[edit | edit source]