Electrolytes and Osmolality

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Electrolytes and Osmolality
2013-05-05 21:58:23
Calcium Phosphorus Magnesium Iron TIBC

Calcium, Phosphorus, Magnesium, Iron, TIBC
Show Answers:

  1. What forms does calcium exist and which is biologically active?
    • 50% Free (ionized) - Biologically active
    • 40% Bound to protein
    • 10% Bound to anions
  2. What do decreased levels of free (ionized) calcium cause?
    Muscle spasms or uncontrolled muscle contractions - called tetany
  3. What causes tetany?
    Decreased levels of free (ionized) calcium
  4. How is serum calcium regulated?
    • Parathyroid hormone
    • Vitamin D
    • Calcitonin
  5. What happens when there is a decrease in free (ionized) calcium?
    Decrease in free (ionized) calcium stimulates the release of PTH by the parathyroid gland
  6. What happens when there is an increase in free (ionized) calcium?
    Rise in free (ionized) calcium terminates PTH release
  7. In bone, what does PTH do?
    In bone, PTH activates osteoclasts to break down bone with the release of calcium
  8. In the kidneys, what does PTH do?
    In the kidneys, PTH increases tubular reabsorption of calcium and stimulates hydroxylation of vitamin D to the active form
  9. How is Vitamin D used?
    • Initially, vitamin D is transported to the liver where it is hydroxylated - but still inactive
    • The hydroxylated form is transported to the kidneys, where it is converted to 1,25-dihydroxycholecalciferol - the active form
  10. How is calcium absorption enhanced?
    • In the intestines, it is enhanced by vitamin D
    • In the kidneys, PTH increases tubular reabsorption
  11. What releases calcitonin?
    Parafollicular cells of the thyroid gland when serum calcium level increases
  12. What does calcitonin do?
    Inhibits vitamin D and parathyroid hormone activity - decreasing serum calcium
  13. What causes an increase level of calcitonin?
    Medullary carcinoma of the thyroid glandĀ (neoplasm of the parafollicular cells)
  14. What causes hypercalcemia?
    • Primary hyperparathyroidism
    • Other endocrine disorders (hypothyroidism and acute adrenal insufficiency)
    • Malignancy involving bone and renal failure
  15. What causes hypocalcemia?
    • Hypoparathyroidism
    • Hypoalbuminemia
    • Chronic renal failure
    • Magnesium deficiency
    • Vitamin D deficiency
  16. How is free (ionized) serum calcium measured?
    • Ion-specific electrode measures free form
    • Measurement is temperature sensitive (generally 37 degrees celcius)
  17. What is the reference range of total calcium?
    8.6-10.3 mg/dL
  18. What is the reference range of free (ionized) calcium?
    4.6-5.3 mg/dL
  19. How is phosphate regulated?
    • Phosphate in the blood is absorbed from dietary sources, released from cells, or released from bone
    • Regulation occurs by reabsorption or excreation by the kidneys
    • PTH increases renal excretion of phosphate
    • Vitamin D regulates phosphate by causing intestinal absorption and renal reabsorption
  20. What causes hyperphosphatemia?
    • Renal failure
    • Hypoparathyroidism
    • Neoplastic diseases
    • Lymphoblastic leukemia
    • Intense exercise
  21. What causes hypophosphatemia?
    • Diabetic ketoacidosis
    • Hyperparathyroidism
    • Asthma
    • Alcoholism
    • Malabsorption syndrome
  22. What is the reference range of Phosphorus?
    2.5-4.5 mg/dL
  23. How does magnesium exist in plasma and which is biologically active?
    • 55% Free (ionized) - biologically active
    • 30% Bound to protein
    • 15% Complexed
  24. How is magnesium regulated?
    • Regulated by the kidneys through reabsorption and excretion
    • PTH enhances reabsorption by the kidneys and intestinal absorption
  25. What causes hypermagnesemia?
    • Renal failure
    • Excess antacids
  26. What causes hypomagnesemia?
    • Gastrointestinal disorders
    • Renal diseases
    • Hyperparathyroidism (hypercalcemia)
    • Drugs (diuretic therapy, cardiac glycosides, cisplatin, cyclosporine)
    • Diabetes mellitus with glycosuria
    • Alcoholism due to dietary deficiency
  27. What is the reference range of magnesium?
    1.7-2.4 mg/dL
  28. Where is iron found in the body?
    • Component of hemoglobin and myoglobin (ferritin and hemosiderin)
    • Tissue compartment (component of enzymes and coenzymes)
    • Labile pool
  29. How is iron transported in the blood?
  30. What is the term for having values being highest in the morning and iron exhibits this?
    Diurnal variation
  31. What causes an increase of transferrin?
    Iron-deficiency disorders
  32. What causes a decrease of transferrin?
    • Iron overload
    • Hemochromatosis
    • Severe infections
  33. What is the reference range of trasferrin?
    200-360 mg/dL
  34. What does ferritin reflect?
    Reflects iron stores
  35. What causes a decrease in ferritin?
    Iron deficiency disorders
  36. What causes an increase in ferritin?
    • Iron overload
    • Hemocharomatosis
    • Severe infections
  37. What are the reference range for ferritin?
    • Males: 20-250 ng/mL
    • Females: 10-120 ng/mL
  38. What is associated with decreased serum iron?
    • Iron deficiency anemia
    • Malnutrition
    • Blood loss
    • Chronic infection
  39. What is associated with increased serum iron?
    • Iron overdose
    • Sideroblastic anemia
    • Viral hepatitis
    • Hemochromatosis
  40. What is the calculation to calculate % transferrin saturation?
  41. What is the reference range of serum iron?
    45-160 micro-gram/dL
  42. What is the reference range of TIBC?
    250-425 micro-gram/dL
  43. What is the reference range of % saturation?