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Hormonal Cascade System

Hormonal Cascade System. Connection of hypothalamus and pituitary. Hypothalamus to anterior pituitary to ultimate glands. Releasing hormones Amplification of signal Negative feedback. Posterior pituitary. Some Major Hormones of Anterior Pituitary. Hormone Action

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Hormonal Cascade System

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  1. Hormonal Cascade System Connection of hypothalamus and pituitary

  2. Hypothalamus to anterior pituitary to ultimate glands • Releasing hormones • Amplification of signal • Negative feedback • Posterior pituitary

  3. Some Major Hormones of Anterior Pituitary Hormone Action Thyrotropin (TSH) T4 and T3 release from thyroid Luteinizing hormone (LH) Testosterone synthesis in Leydig cells Progesterone synthesis in corpus luteum Follicle-stimulating Spermatogenesis in Sertoli cells hormone (FSH) Estradiol synthesis in ovary; ovum maturation Adrenocorticotropic Cortisol synthesis in adrenal cortex hormone (ACTH)

  4. Synthesis of Peptide Hormones • Proopiomelanocortin is precursor polypeptide for eight hormones • Other genes encode only one hormone

  5. Thyroid Hormone • Iodination of tyrosine residues in thyroglobulin • Proteolysis releases T3 and T4

  6. Epinephrine • Adrenal medulla • Derived from tyrosine or phenylalanine • Targets hepatocytes and vascular smooth muscle cells

  7. Begin with tyrosine or phenylalanine; hydroxylations • Norepinephrine converted to epinephrine by PNMT

  8. Neuronal and glucocorticoid regulation

  9. Steroid Hormones • Adrenal cortex, ovary and testes • Derived from cholesterol • Cyclopentanoperhydro-phenanthrene nucleus • Act on nuclear receptors

  10. Steroid Biosynthesis • Begin by forming D5-pregnenolone • Further modifications for specific steroids • Involves cytochrome P450's

  11. Control of Steroid Synthesis • Cell surface receptor activated • Stimulate conversion of cholesterol

  12. Hormones that Stimulate Synthesis of Steroid Hormones Steroid Hormone-producing Hormone Structure Signal Cortisol Adrenal cortex ACTH Aldosterone Adrenal cortex Angiotensin II/III Testosterone Leydig cell LH Estradiol Ovarian follicle FSH Progesterone Corpus luteum LH 1,25(OH)2 D3 Kidney Parathyroid hormone (PTH)

  13. Adrenal Hyperplasia • 21-hydroxylase deficiency • Lack of cortisol and aldosterone • Buildup of androgens • Masculanization • Treated with cortisol

  14. Actions of Steroid Hormones Hormone Target Tissue/Effects Progesterone Uterine endometrium, mammary Estradiol Female: gonadotropin secretion, uterine endometrium Male: inhibit testosterone synthesis Testosterone Male: converted to dihydrotestosterone, Sertoli cells, secondary sex characteristics Cortisol Stress adaptation, elevate liver glycogen, suppress immune responses Aldosterone Kidney, Na+ reabsorption to raise blood pressure

  15. Vitamin D Synthesis • D3 produced in skin • Further hydroxy-lations to form active 1,25-(OH2)D

  16. Control of Serum Calcium Levels • PTH produced in response to low serum calcium • Synthesis of 1,25-(OH2)D induced by PTH • 1,25-(OH2)D responsive genes in intestinal epithelial

  17. 1,25-(OH2)D and PTH act together in response to low serum calcium • High serum calcium calcium decreases PTH, inactive 24,25(OH2)D synthesized

  18. Vitamin D Deficiency and Toxicity Deficiency • Rickets • Improper bone and cartilage formation Toxicity • Hypercalcemia • Calcification in tissues, soft bones

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