Gigantism
Gigantism is a non-specific term that refers to enlargement of normal body proportions and can be divided into generalized gigantism (i.e. of the whole body) or localized gigantism (i.e. affecting only part of the body).
Localized gigantism is due to a variety of causes, and is discussed separately.
The etiology of gigantism will clearly depend on the definition. If one uses the term broadly, merely referring to a height two or more standard deviations above an age, gender and Tanner stage matched cohort, then most cases will merely be physiological tallness . In contrast, by far the most common cause of pathological gigantism is the presence of growth hormone secreting pituitary adenoma (a.k.a. pituitary gigantism), which is the focus of the remainder of this article.
Note: for gigantism to occur, growth hormone excess needs to occur before growth plates are fused. If this occurs later in life, then stature will not be affected and individuals develop acromegaly.
Epidemiology
The vast majority of cases of pituitary gigantism are sporadic, and diagnosed in mid to late childhood (e.g. 13 years of age ).
Rare genetic mutations (e.g. X-linked acrogigantism) are recognized .
Clinical presentation
Clinical presentation is typically, not surprisingly, due to noticeable excessive height, although due to the positive societal attitude towards tall people, particularly in males, can lead to delay in investigation.
Radiographic features
Bone age assessment is very helpful in assessing skeletal size and maturity.
Increased stature is fairly obvious clinically but may be inapparent on radiography.
Cross-sectional imaging demonstrates similar features to those seen in acromegalic patients, and is discussed there.
Treatment and prognosis
Treatment of gigantism can be challenging, as transsphenoidal surgery (which is considered first line therapy) often does not control growth hormone levels . Additional therapeutic options include medical therapy (e.g. with octreotide and/or pegvisomant) and radiotherapy .
