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The hook effect refers to the prozone phenomenon, also known as antibody excess, or the postzone phenomenon, also known as antigen excess. It is an immunologic phenomenon whereby the effectiveness of antibodies to form immune complexes can be impaired when concentrations of an antibody or an antigen are very high.
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 .
Mice without a posterior pituitary do not raise their prolactin levels even with suckling and oxytocin injection, but scientists have yet to identify which specific hormone produced by this region is responsible. [45] In birds (turkeys), VIP is a powerful prolactin-releasing factor, while peptide histidine isoleucine has almost no effect. [46]
The pituitary gland is divided into three lobes: the anterior pituitary, the intermediate pituitary lobe, and the posterior pituitary. The hypothalamus controls the anterior pituitary's hormone secretion by sending releasing factors, called tropic hormones , down the hypothalamo-hypophysial portal system. [ 3 ]
The anterior pituitary (also called the adenohypophysis or pars anterior) is a major organ of the endocrine system.The anterior pituitary is the glandular, anterior lobe that together with the (posterior pituitary, or the neurohypophysis) makes up the pituitary gland (hypophysis) which, in humans, is located at the base of the brain, protruding off the bottom of the hypothalamus.
For example, high prolactin levels could result from diseases affecting the hypothalamus and pituitary gland. [2] Other organs, such as the liver and kidneys, could affect prolactin clearance and consequently, prolactin levels in the serum. [2] The disruption of prolactin regulation could also be attributed to external sources such as ...
There is a pituitary portal system, with which the hormones are transported. These hormones are prolactin, growth hormone, TSH, adrenocorticotropic hormone, FSH and LH. They are all released by anterior pituitary. Some have targets in glands and some with direct function. Anterior pituitary is an amalgam of hormone producing glandular cells.
The pineal gland is located in the diencephalon of the brain. It primarily releases melatonin, which influences daily rhythms and may have an antigonadotropic effect in humans. [citation needed] It may also influence the melanotropes and melanocytes located in the skin. [citation needed]