Hypothalamic–pituitary–somatotropic axis Hypothalamic–pituitary–somatotropic axis The hypothalamic–pituitary–somatotropic axis (HPS axis), or hypothalamic–pituitary–somatic axis, also known as the hypothalamic–pituitary–growth axis, is a hypothalamic–pituitary axis which includes the secretion of growth hormone (GH; somatotropin) from the somatotropes of the pituitary gland into the circulation and the subsequent stimulation of insulin-like growth factor 1 (IGF-1; somatomedin-1) production by GH in tissues such as, namely, the liver. Other hypothalamic–pituitary hormones such as growth hormone-releasing hormone (GHRH; somatocrinin), growth hormone-inhibiting hormone (GHIH; somatostatin), and ghrelin () are involved in the control of GH secretion from the pituitary gland. The HPS axis is involved in postnatal human growth. Individuals
Pituitary adenoma showed that acromegaly cases with "AIP" mutations occurred about 20 years before acromegaly cases without "AIP" mutations and these tumors are large and relatively treatment resistant. Due to their young age at onset, "AIP" mutations are the most frequent genetic cause of pituitary gigantism (29% of cases). X-LAG is a rare syndrome of very early childhood onset pituitary tumors/hyperplasia that leads to growth hormone excess and severe overgrowth and pituitary gigantism. Three FIPA families with X-LAG have been reported to date all of which had transmission of a chromosome Xq26.3 duplication from affected mother to affected son . The disease