Abstract
GH-secreting pituitary adenomas can cause gigantism or acromegaly, determined by onset before or after epiphyseal fusion of the distal ends of the radius and ulna. Overlapping phenotypes can occur when the condition presents peripubertally. Gigantism is associated with identifiable hereditary causes and genetic mutations in almost 50% of cases; genetic testing should be considered in patients with gigantism and early-onset acromegaly, especially (but not only) when pituitary tumors have aggressive features and/or are refractory to standard treatments. Here, we present a case of a young adult with a giant somatotroph adenoma resistant to multiple treatment modalities and negative for mutations in AIP, which encodes aryl hydrocarbon receptor-interacting protein.