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 functionally connected to the brain, the pituitary gland sits outside the blood–brain barrier. It is separated from the subarachnoid space by the diaphragma sella, therefore the arachnoid mater and thus cerebral spinal fluid cannot enter the sella turcica. The pituitary gland is divided into two lobes, the anterior lobe (which accounts for two thirds of the volume of the gland), and the posterior lobe (one third of the volume) separated by the pars intermedia. The posterior lobe (the neural lobe or neurohypophysis) of the pituitary gland is not, despite its name, a true gland. The posterior lobe contains axons of