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Meghan Ellis

Meghan Ellis. Calcium and Phosphorus Metabolism in Reptiles. Clinical Importance. More than 3.9 million US households with 1+ reptile pets Ca and P derangements are common in pet reptiles Preventable with proper husbandry Treatable with early intervention. Calcium Importance.

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Meghan Ellis

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  1. Meghan Ellis Calcium and Phosphorus Metabolism in Reptiles

  2. Clinical Importance • More than 3.9 million US households with 1+ reptile pets • Ca and P derangements are common in pet reptiles • Preventable with proper husbandry • Treatable with early intervention

  3. Calcium Importance • Cell signaling • Neural transmission • Muscle function • Blood coagulation • Enzymatic co-factor • Membrane and cytoskeletal functions • Bone mineralization

  4. Calcium Regulation

  5. Parathyroid Gland

  6. PTH Regulation • Decreased serum ionized calcium increased synthesis and secretion of PTH from chief cells • Increased serum ionized calcium negative feedback loop • Increased phosphorus decreased serum Ca stimulation of PTH increased renal excretion of phosphorus

  7. Metabolic Functions of PTH • Activate osteoclasts mobilizes calcium from bone • Increase renal tubular reabsorption of calcium • Increases conversion of vitamin D to active dihydroxy form in kidneys • Augments GI calcium absorption

  8. Metabolic Functions of Calcitonin • Promotes absorption of calcium by skeletal system • Inhibits resorption of bone by osteoclasts

  9. Calcitonin Regulation • Increased serum ionized calcium increased synthesis and secretion of calcitonin by C cells of thyroid gland • Decreased serum ionized calcium negative feedback loop

  10. Thyroid Gland

  11. Phosphorus Importance • Bone mineralization • Phospholipid in cellular membranes • Cellular respiration • Component of DNA and RNA • Post-transcriptional modification of proteins

  12. Phosphorus Regulation

  13. Vitamin D3 • Stimulates calcium and phosphorus absorption by intestinal mucosa • Maintains calcium and phosphorus balance for optimal bone mineralization

  14. Calcium Clinical Pathology • Normal total serum calcium: 8-11mg/dL in most reptiles • Normal ionized calcium in Green Iguana: 1.47 +/- 0.104 mmol/L

  15. Hypocalcemia (<8.0 mg/dL) • Dietary deficiency • Excessive dietary phosphorus • Secondary nutritional hyperparathyroidism • Vitamin D3 deficiency (dietary or lack of UV light) • Hypoablbuminemia • Hypoparathyroidism

  16. Hypercalcemia (>20mg/dL) • Excessive dietary calcium and vitamin D3 • Primary hyperparathyroidism • Pseudohyperparathyroidism • Osteolytic bone disease • Vitellogenesis (physiologic)

  17. Phosphorus Clinical Pathology • Normal serum phosphorus: 1-5mg/dL

  18. Hypophosphatemia • Starvation • Nutritional deficiency

  19. Hyperphosphatemia (>5mg/dL) • Excessive dietary phosphorus • Hypervitamintosis D3 • Renal disease • Severe tissue trauma • Osteolytic bone disease • Sample handling error

  20. Nutritional Secondary Hyperparathyroidism • Cause: diet low in calcium or vitamin D3, diet high in phosphorus, lack of exposure to UV-B light • Pathogenesis: Low serum Ca PTH secretion increased bone resorption, increased renal absorption of Ca and increased excretion of PO4, stimulation of 1,25-dihydroxycholecalciferol which increases GI absorption of Ca increase serum calcium and decrease serum PO4

  21. NSHP Effects • Hypocalcemia neural hyperexcitability twitching digits, hyperreflexia, ataxia, disorientation, cloacal prolapse • Increased osteoclastic osteolysis demineralization of bone fractures of long bones and spine, thickening and swelling of long bones and mandibles, “rubber jaw”

  22. NSHP Effects continued • Effects on reproduction: decreased calcification of egg shells weak rubbery eggs • Clinical Pathology: low normal serum calcium; increased PTH

  23. NSHP

  24. NSHP Treatment • Correct hypocalcemia • Rehydrate • Correct Husbandry

  25. Renal Secondary Hyperparathyroidism • Cause: chronic renal disease- degenerative nephroses due to inadequate husbandry, poor nutrition, NSHP • Pathogenesis:failure of kidneys to excrete excess phosphorus decreased serum Ca due to Ca X P rule PTH secretion • Hyperphosphatemia renal tubular cells cannot hydroxylate 25-hydroxycholecalciferol to active vitamin D3 increased PTH secretion • Decreased vitamin D3 no GI absorption of Ca

  26. RSHP Effects • Crispy critters: Ca x P >9  mineralization of kidneys; >12 mineralization of other soft tissues especially GI and cardiorespiratory systems • Ischemic necrosis of tail, vomiting, passing poorly digested food, congestion of peripheral blood vessels especially obvious in sclera • All the signs of hypocalcemia

  27. RSHP

  28. RSHP Clinical Pathology • Hyperphosphatemia • Low or low normal serum calcium • Dehydration • Nonregenerative anemia • Inverted Ca:P ratio (should be 1.2-2:1) • Increased PTH • Iohexol clearance study for GFR estimate

  29. Other Methods • Renal biopsy • Ultrasound • Radiograph

  30. RSHP Treatment • Usually present in end-stage renal failure • Reduce dietary protein • Correct hyperphosphatemia • Correct hypocalcemia • Correct and prevent dehydration • Supplement vitamin B complex • Omega-6: Omega-3 = 3:1 • Correct husbandry

  31. The End

  32. References • Robbins and Cotran Pathologic Basis of Disease 7th ed • Nelson and Couto Small Animal Internal Medicine 3rd ed • Mader Reptile Medicine and Surgery • Hernandez-Divers, Stephen et al “Renal evaluation in healthy green iguanas (Iguana iguana): assessment of plasma biochemistry, glomerular filtration rate, and endoscopic biopsy.” Journal of Zoo and Wildlife Medicine June 2005; 36(2):155-168

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