Definition
A small endocrine gland at the base of the brain that releases growth hormone, ACTH, TSH and other hormones.
The pituitary gland sits in a bony cavity beneath the hypothalamus and is connected to it by a stalk. Its anterior lobe contains specialised cells that secrete growth hormone (somatotrophs), prolactin, ACTH, TSH, LH and FSH, each under hypothalamic control. Its posterior lobe stores and releases oxytocin and vasopressin, which are made by hypothalamic neurons. Because it integrates signals from the brain with feedback from target organs, the pituitary is central to endocrine research. Growth hormone release, for example, is driven by GHRH, inhibited by somatostatin and amplified by ghrelin-receptor agonists, which makes somatotrophs the main site of action for growth hormone secretagogue peptides.