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Role of Calcitonin and Parathormone in Calcium Homeostasis Control

Learn about Calcitonin and Parathormone produced by endocrine glands in the pharyngeal region. Explore their functions, mechanisms, and regulation in controlling calcium levels. Discover how these hormones interact with other factors to maintain calcium balance in the body.

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Role of Calcitonin and Parathormone in Calcium Homeostasis Control

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  1. Phayrngeal Region Endocrine Glands Parathyroid Control of Calcium Homeostasis

  2. Phayrngeal Region Endocrine Glands • Calcitonin • Produced in the intrafollicular cells of the thyroid • Produced by C-cells that are present in the thyroid, thymus, and parathyroid • Chemistry • Single chain protein 32 amino acids • Entire molecule required for biological activity 3-12

  3. Phayrngeal Region Endocrine Glands • Calcitonin • Function • Lowers circulating Ca+ • Targets bone, kidney, gut • Lowers ca by • Blocking absorption in the gut • Promoting its excretion in the kidney • Depositing it on the bone 3-22

  4. Phayrngeal Region Endocrine Glands • Calcitonin • Regulation and secretion • No neural or neuroendocrine regulation • Calcium level is the most important regulator • Other hormones stimulate it CCK, gastrin 3-22

  5. Regulation of Ca PTH CT Normal Ca level 3-22 9.5 mg % 11 mg % [Ca+]

  6. Phayrngeal Region Endocrine Glands • Parathyroid • Anatomy • Embedded in surface of thyroid • Removal leads to death • Chief cells make PTH • Parathormone • Single chain 84 amino acids • Active core of 34 AA’s 3-8

  7. Phayrngeal Region Endocrine Glands • Parathormone • Functions • Maintains Ca in body • Essential for life • Not stored, used readily • Supports all functions requiring Ca • muscular and nervous function • Bone structure • Blood clotting • 2nd messenger systems • Egg shells 3-22

  8. Phayrngeal Region Endocrine Glands • Parathormone • Mechanisms • Increase or decrease: • deposition in bone • Absorption in kidney and GI tract • Primary control • Calcitonin, vitamin D3, PTH • Secondary control • Adrenal steroids, thyroid 3-22

  9. Ca balance • Total body Ca = 1.0-1.5Kg Ca • Tissues = 12g • Body fluids =1g (50% bound) • 99% is in the bone! • Bone is a major Ca reservoir • 1% readily availible • 99% slowly available

  10. Ca balance • Pathways • Gut • Kidney • Liver • Ovary • Hormones • PTH, Calcitonin,Vitamin D3

  11. Ca balance • Vitamin D3 • Works primarily on GI tract • Secondarily on the Bone • Source = Diet and Sunlight • PTH and Vitamin D are intimately related • Precursor is cholesterol • Fig 9.6, 9.8

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