There are two main types of growth disorders: excessive growth and growth hormone deficiency.
Acromegaly is the most common disorder of excess growth hormone secretion, caused by hypersecretion of IGF-I. In contrast to gigantism, it occurs in adolescence and adults after their epiphyseal growth plates have fused.
The symptoms of acromegaly vary and can develop gradually over time. Early detection of acromegaly is key, as the pathological effects of increased growth hormone production are progressive. IGF-I provides the most sensitive lab test for the diagnosis of acromegaly.
Gigantism is also an excessive action of IGF-I, but occurring whilst epiphyseal growth plates are open. This is a very rare disorder which affects both children and adolescents with gigantism stand > 2 standard deviations above the mean height for their gender and age.
Growth Hormone Deficiency
Growth hormone deficiency means the pituitary gland does not make enough growth hormone. The cause of growth hormone deficiency is mainly unknown. It may be present at birth or develop later as a result of an injury or medical condition. Severe brain injury may also cause growth hormone deficiency. Slow growth may first be noticed in infancy and continue through childhood. Although uncommon, growth hormone deficiency may also be diagnosed in adults. Possible causes include tumours involving the pituitary gland or hypothalamus, or brain radiation treatments for cancer.