Gigantism is a rare pediatric disorder defined by excess growth hormone that occurs before the completion of the normal ossification process. This results in tall adult stature due to unrestrained long bone growth.

The etiology of gigantism is not well understood. Some patients have underlying genetic mutations leading to excess growth-hormone production, while others can have growth-hormone secreting tumors (although this is less common in children). Gigantism can be an isolated finding or present as part of a syndromic phenotype, such as McCune-Albright syndrome or multiple endocrine neoplasia (MEN) type 1 and MEN type 4. It is more common in males.

Patients present with accelerated linear growth and macrocephaly with a lag in weight gain. There is no uniform phenotype for patients with gigantism, but coarse facial features and large hands and feet have been described in several patients.