Lecture 1 and 2 ANTERIOR and POSTERIOR PITUITARY.pptx - ANTERIOR PITUITARY Hypothalamic Pituitary Axis ADRENOCORTICOTROPIC HORMONE \u2022 ACTH-secreting

Lecture 1 and 2 ANTERIOR and POSTERIOR PITUITARY.pptx -...

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ANTERIOR PITUITARY
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Hypothalamic Pituitary Axis
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ADRENOCORTICOTROPIC HORMONE ACTH-secreting corticotrope cells constitute bout 20% of the pituitary cell population. ACTH (39 ino cids) is derived from the POMC precursor protein (266 amino cids) that also generates sever l other peptides, including β-lipotropin, β- endorphin, met-enkephalin, α-melanocyte-stimulating hormone (α-MSH), and corticotropin-like intermediate lobe protein (CLIP). Target gland: adrenals (induces steroid production) Secretion agonists: CRH, AVP, proiniflammatory cytokines Secretion antagonists: glucocorticoids (negative feedback)
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GROWTH HORMONE GH-secreting somatotrope cells constitute up to 50% of the total anterior pituitary cell population. Target organs: liver (IGF-I production), bone (growth induction), other tissues (insulin antagonism). Secretion agonists: GHRH, Ghrelin Secretion antagonists: Somatostatin , IGF-I – via negative feedback.
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PROLACTIN PRL is synthesized in lactotropes, which constitute about 20% of anterior pituitary cells. Target organ: breast (induces milk production). Weak secretion agonists: Estrogen, TRH, VIP Secretion antagonist: Dopamine
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THYROID-STIMULATING HORMONE TSH-secreting thyrotrope cells constitute 5% of the anterior pituitary cell population. Target gland: thyroid (induces thyroid hormone synthesis). Secretion agonist: TRH Secretion antagonists: T3, T4, dopamine, somatostatin, glucocorticoids.
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GONADOTROPINS: FSH AND LH Gonadotrope cells constitute about 10% of anterior pituitary cells and produce two gonadotropin hormones— LH and FSH. Target organs: ovary - FSH induces follicle growth and estrogen production, LH induces ovulation and maintenance of corpus lutheum; testis – LH induces Leydig cell testosterone synthesis and secretion, FSH stimulates seminiferous tubule development and regulates spermatogenesis. Secretion agonists: GnRH, Estrogen. Secretion antagonists: Sex steroids, inhibin (negative feedback).
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Diagnostic Tests Stimulation Tests i/v L- arginine, L-Dopa, GHRH and Insulin tolerance tests for GH stimulation ITT, CRH, AVP and Metyrapone tests for ACTH stimulation Suppression Tests OGTT for GH supression 1 mg Dx test High dose Dx Test
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HYPOPITUITARISM Congenital Transcription factor defect Pituitary dysplasia/aplasia Primary empty sella Septo-optic dysplasia, Prader-Willi syndrome, Laurence-Moon-Biedl syndrome, Kallmann syndrome Aquired Traumatic (surgery, radiation, head injury).
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  • Winter '20
  • Jane Smith
  • Pituitary adenoma

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