Pituitary function test useful in the diagnosis of hypothalamic disorder, hypopituitarism, acromegaly, and ectopic growth hormone production by neoplasm. hGH is physiologically important in two main areas. Firstly, it has an integral role in skeletal growth which is well demonstrated in either excess or deficiency in childhood. Secondly, hGH influences intermediary metabolism by stimulating lipolysis and is antagonistic to the insulin- mediated uptake of glucose. hGH secretion is stimulated by hypoglycemia and suppressed by hyperglycemia. In childhood, symptoms of hGH deficiency are retarded growth and dwarfism. Etiology is often unknown and an absolute or relative deficiency usually becomes apparent at about 2 years of age. Diagnosis can be confirmed by demonstrating low serum hGH which does not respond to stimulation tests. hGH deficiency is a major cause of severe short stature and diagnosis at an early stage is essential for successful therapy. In childhood, excess hGH is characterized by gigantism. In adults, excess hGH results in acromegaly, a condition characterized by progressive thickening of bone and soft tissue.