Auxologic criteria (defined by body measurements) Indirect hormonal criteria (IGF levels from a single blood sample) Direct hormonal criteria (measurement of GH in multiple blood samples to determine secretory patterns or responses to provocative testing), in particular: Subnormal frequency and amplitude of GH secretory peaks when sampled over several hours Subnormal GH secretion in response to at least two provocative stimuli Increased IGF1 levels after a few days of GH treatment Response to GH treatment Corroborative evidence of pituitary dysfunction