Mineral Metabolism Flashcards
Function of Calcium
Ionized Calcium is the physiological active form
Important co-enzyme in coagulation cascade
Role in heart, muscle, and nerve excitability
Suppresses neuromuscular excitability
Plays a role in transport across membranes
Structure and Concentration of Calcium
99% located in bone as CaPo4 complex
- Hydroxyapatite
Location of Calcium in body
Bone - 99%
Other sites - 1%
Calcium Analysis
Two types of tests
Total serum calcium
Protein bound (albumin and globulins)
Complexed to ions (Citrate, phosphate, bicarbonate, sulfate)
Ionized Ca2+
Phosphorus Function
Tied up with calcium in skeleton
Other Functions:
- High intracellular phosphate concentration
- Carbohydrate metabolism: ATP
- Component of nucleic acids, phospholipids, and nucleotides
- Phosphate buffer important in balancing acid in urine
Magnesium Function
Found in 50% of bone with calcium and phosphorus
Rest is found with potassium inside cell
Acts as a co-enzyme in enzyme reactions
Regulation not fully understood
Elevated Magnesium
Intoxication
Renal Failure - unable to filter appropriately
Low Magnesium
Impaired absorption or intake
Excessive renal loss
Organs Involved in regulation of Ca and PO4
Parathyroids
Thyroid
Kidneys
Liver
Skeletal system
Intestine
Parathyroid Produces
PTH (Parathyroid Hormone)
Regulating Calcium and Phosphorus Concentrations
Thyroid Produces
C-cells
Calcitonin
Kidneys Function for Ca and PO4
Hydroxylate Vitamin D
Control Ca and PO4 absorption
Liver Creates
Hydroxylated Vit D
Parathyroids Info
Lobe of the thyroid gland
4 glands are present
Calcitonin
Produced by C-cells of Thyroid
Acts antagonistically to PTH
Stimulated by elevated Ca2+
Found in children who also have high Alkaline Phosphatase
Responsible for laying down crystalline bone
Bone and ECF ions are in balance with one another
Osteoclasts
Osteoblasts
Osteoclasts
Involve in bone resorption
PTH breaks down CaPO4 component
Osteoblasts
Involved in bone formation
Calcitonin creates when too much Ca2+ in serum
Vitamin D
Steroid hormone made from cholesteroal
Governs absorption of Ca2+ from GI tract
Activated by low serum Ca2+
Activates formation of carrier protein for Ca2+
Vitamin D Conversion
Active form undergoes two conversions
- First in liver
- Second in kidneys
Kidneys also actively secrete phosphates and reabsorb Ca2+
Hypocalcemia caused
Hypoparathyroidism
- Serum calcium = Decreased
- Serum Phosphorus = Increased
- Urine Calcium = Decreased
- Urine Phosphorus = Decreased
- PTH = decreased
Hypocalcemia Hypoparathyroidism Complications
Twitching
Tetany
Convulsions
- Common cause: Thyroid surgery
Hypocalcemia Vitamin D Deficiency
PTH is working fine, but no Vit D to absorb
- Serum Calium = Decreased
- Serum Phosphorus = Decreased
- Urine Calcium = Decreased
- Urine Phosphorus = Increased
- PTH = Increased
Hypocalcemia Vit D Deficiency Complications
Rickets (prior to puberty)
Osteomalacia (after puberty) - fractures and bowing of bone
Causes:
- Inadequate sunlight
- Inadequate dietary source
- Kidney disease
Hypocalcemia Chronic Renal Failure
Serum Calcium = Decreased
Serum Phosphorus = Increased
PTH = Increased
Urine Calcium = Decreased
Urine Phosphorus = Decreased
Hypocalcemia Complications
Decreased Serum Calcium: Tetany, bone lysis
Secondary Hyperparathyroidism
Hypercalcemia Primary Hyperparathyroidism
Serum Calcium = Increased
Serum Phosphorus = Normal to Decreased
PTH = Increased
Urine Calcium = Increased
Urine Phosphates = Increased
Hypercalcemia Primary Hyperparathyroidism Complications
Bone lysis
Kidney stones
Cause: Adenoma of parathyroid gland
Hypercalcemia Hypervitaminosis D
Serum Calcium = Increased
Serum Phosphorus = Normal to Increased
PTH = Normal to Decreased
Urine Calcium = Increased
Urine Phosphorus = Decreased
Hypercalcemia Hypervitaminosis D Complications
Kidney Stones
Metastatic Calcification
Renal Failure
Hypercalcemia Bone Malignancy
Serum Calcium = Increased
Serum Phosphorus = Normal, Increased, or Decreased
PTH = Normal to Decreased PTH
Urine Calcium = Increased
Urine Phosphorus = Increased
Hypercalcemia Bone Malignancy Complications
Bone Fractures
Cause: Invasive tumors of multiple myeloma and breast carcinoma
Metabolic Bone Disease
Paget’s Disease (Ostetitis Deformans)
Paget’s Disease Frequency
3% incidence in those over 40 yrs
Paget’s Disease General Info
Unknown cause
Bone Resorption = Increased
Osteoclast Activity = Increased
Bone formation = Increased
- Deposition is irregular and haphazard
Alkaline Phosphatase = Increased
Ca = Normal to Rarely Increased
Phosphorus = Normal to Rarely Increased
Osteoporosis
Loss of bone density with age
General Change in balance mechanism related to hormones and life risk factors
Osteoporosis Risk Factors
Advanced Age
Women more effected
Perimenopause
Decreased Ca intake
Cigarette smoking
Carbonated Soda
Hyperphosphatemia (Increased levels of Phosphate)
Hypoparathyroidism (low PTH levels)
Vitamind D Intoxication (increased intestinal absorption)
Renal Insufficiency
Failure to filter phosphates
Hypophosphatemia (Decreased levels of Phosphate)
Primary or Secondary Hyperparathyroidism
- Primary - tumor keeps producing PTH
- Secondary - renal as PTH is increased but kidneys not responding
Vitamin D deficiency
Malabsorption syndrome
Renal excretion - Primary or Secondary
Total Calcium Assay
Dye binding or color complex method
Calcium complexes with dye to cause color change
Arsenazo III
o-cresolphathalein complexone
- Magnesium interference eliminated by adding 8-hydroxy quinoline
Ionized Calcium Assay
Measured with ion-selective electrode
Ionized Calcium Calculation
((6 x Total Calcium) - (1/3 x Total Protein)) / (Total Protein +6)
Phosphorus Assay
Phosphate ions complex with molybdate to form phosphomylbdate which gives a color change when reduced to phosphomolybdate
