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Endocrinology 2 - Endocrinology Test 2 7 hypothalamic...

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Endocrinology Test 2 7 hypothalamic hormones released via portal system into A. Pituitary (aka adenohypophysis) 5 target cells for 7 hypotalamic hormones 2 types of cells o 2 cell types – acidophilic o 3 cell types – basophilic Acidophilic o Lactotrophs (mammatotrophs) – respond to PRH/PIH o Somatotrophs – respond to GHRH/GHIH Basophilic o Thyrotrophs – respond to TRH o Corticotrophs – respond to CRH o Conadotrophs – respond to GnRH Lactotrophs Target cell for PRH/PIH o PRH binds to PRH receptors to stimulate production and release of hormone Prolactin The major stimuli for prolactin release 1. Pregnancy a. Hormones specifically (projesterone, estrogen, human placental lactogen) stimulate prolactin release 2. Nipple stimulation (suckling) a. Sets up (+) feedback mechanism via neuroendocrine reflex that stimulates synthesis and release of prolactin from lactotrophs b. Suckling elicits release of oxytocin and prolactin 3. Seizure activity a. May involve same neuroendocrine reflex used by suckling of infant 4. Dopamine Antagonist a. Antipsychotic drugs that act by blocking Dopamine results in high levels of prolactin being release 5. Primary hypothyroidism a. Where thyroid gland fails to produce thyroid hormones. In absence of thyroid hormones, TRH levels rise which causes increase in prolactin release i. Is TRH a PRH? Or are high levels of TRH acting as a PRH? – we say just acting Biological actions of Prolactin o Prolactin binds to prolactin receptors that recruit TK JAK-STAT-MAPK signal transaction mechanism 1. Pregnancy boobs a. During pregnancy, prolactin synergizes with pregnancy hormones to 1
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stimulate breast development for preparation of lactation/breast feeding b. However – during pregnancy, P-hormones inhibit the lactopoietic effect of prolactin so milk production will NOT occur during pregnancy c. Post-partum the levels of pregnancy hormones fall removing inhibition of prolactin d. Lactopoisis occurs 3-4 days post-partum 2. Milk production a. Stimulates mammary (alveolar) glands to produce milk 1. Oxytocin stimulates milk ejection reflex, oxytocin does NOT stimulate milk production PIH o Hypothalamic hormone that inhibits the lactotrophs from releasing prolactin o Same as dopamine Proof: Dopamine antagonists: Prolactin Dopamine agonists (such as bromocriptine): Prolactin Dysfunction o Hyperprolactinemia (hyperfunction) Often caused by A.P. tumor Blocks GnRH receptors turning male female b/c testosterone can’t be made down line o Hypoprolactinemia (hypofunction) Not really a problem except for breast feeding mothers b/c causes milk production during lactation Hyperprolactinemia levels of prolactin in blood Causes o Prolactinomas – cancer tumors of A.P. involving lactotrophs o Dopamine antagonist intake can sometimes cause it Antipsychotic drugs Effects in Males o Gynecomastia – breast development/budding in males o Galactorrhea – milk production in developed breast o
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