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The pituitary gland or hypophysis is an endocrine gland in vertebrates. In humans , the pituitary gland is located at the base of the brain , protruding off the bottom of the hypothalamus . The human pituitary gland is oval shaped , about 1 cm in diameter, 0.5–1 gram (0.018–0.035 oz) in weight on average, and about the size of a kidney bean .
(The hypothalamus and pituitary glands are organs of the neuroendocrine system. One of the most important functions of the hypothalamus—it is located in the brain adjacent to the pituitary gland—is to link the endocrine system to the nervous system via the pituitary gland.)
The hypothalamus produces the hormones oxytocin and vasopressin in its endocrine cells (left). These are released at nerve endings in the posterior pituitary gland and then secreted into the systemic circulation. The hypothalamus releases tropic hormones into the hypophyseal portal system to the anterior pituitary (right).
Synthetic TRH is also used by physicians as a test of TSH reserve in the pituitary gland as it should stimulate the release of TSH and prolactin from this gland. The main releasing hormones are as follows: The hypothalamus uses thyrotropin-releasing hormone (TRH or thyroliberin) to tell the pituitary to release thyrotropin.
The posterior pituitary is not glandular as is the anterior pituitary. Instead, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary, and serve as a site for the secretion of neurohypophysial hormones ( oxytocin and vasopressin ) directly into the blood. [ 2 ]
[citation needed] Sympathetic nerve fiber impulses stimulate the release of adrenal medullary hormones. In this way the sympathetic division of the autonomic nervous system and the medullary secretions function together. The major center of neuroendocrine integration in the body is found in the hypothalamus and the pituitary gland. Here ...
By stimulating GnRH release, kisspeptin indirectly promotes the secretion of LH and FSH from the pituitary gland. Two main populations of kisspeptin neurons have been identified in the hypothalamus: one in the arcuate nucleus (ARC) and another in the anteroventral periventricular nucleus (AVPV) in rodents, or the preoptic area (POA) in humans. [7]
Endocrine disease is characterized by irregulated hormone release (a productive pituitary adenoma), inappropriate response to signalling (hypothyroidism), lack of a gland (diabetes mellitus type 1, diminished erythropoiesis in chronic kidney failure), or structural enlargement in a critical site such as the thyroid (toxic multinodular goitre).