Gigantism is an excessive secretion of growth hormone during childhood, before the closure of the bone growth plates. This excess growth hormone causes overgrowth of the long bones and very tall stature.

The cause of excess growth hormone secretion is most often a benign pituitary gland tumor. Gigantism may also be caused by an underlying medical condition such as multiple endocrine neoplasia type 1 (MEN-1), McCune-Albright syndrome (MAS), neurofibromatosis, or Carney complex.

If excessive secretion of growth hormone occurs after normal bone growth has stopped, the condition is known as acromegaly.

The vertical growth in height that marks this condition is also accompanied by growth in muscles and organs, which makes the child extremely large for his or her age. The disorder can also delay puberty.

Gigantism is very rare.

• Excessive growth during childhood.
• Frontal bossing and a prominent jaw
• Thickening of the facial features
• Disproportionately large hands and feet with thick fingers and toes
• Increased perspiration
• Weakness
• Secretion of breast milk
• Irregular menstruation
• Headache
• Delayed onset of puberty
• Double vision or difficulty with peripheral vision

• An increase in insulin growth factor-I (IGF-I) levels
• A failure to suppress serum growth hormone (GH) levels after an oral glucose challenge (maximum 75g)
• A CT or MRI scan of the head showing pituitary tumor
• High prolactin levels

Other hormone levels may be low due to damage to the pituitary, including thyroid hormone, testosterone (boys), estradiol (girls), or cortisol.