Mg, Ca, PO4, and Bone Disease Flashcards
How much of bone is minerals vs. collogen
2/3 minerals + 1/3 organic collogen material
4 Parts of Bone Anatomy
Periosteum – tough fibrous outer membrane with blood vessels and nerves
Compact Bone – hard tube beneath the periosteum
Spongy Bone – honeycomb structure at end of long bones that provides weight bearing strenght
Marrow – red vs yellow marrow
Red vs. Yellow Marrow
- Red Marrow – produces RBCs in spongy bone of long bones and flat bones of the skull, ribs, pelvis, breast bone, and spine
- Yellow Marrow – fat reserve, in hollow bone shafts (femor/humorus)
Where is PTH produced?
Parathyroid
PTH Functions
PTH activates bone resorption
PTH increases renal re-absorption of Calcium
PTH stimulates renal production of active Vitamin D
excretion of Phosphates
What conditions activate PTH
low serum levels of calciium
What activates Vitamin D?
PTH
Function of Vitamin D
Increases Calcium and Phosphate absorption by intestines
Enhances PTH effect on bone resorption
Where is Calcitonin produced?
thyroid
Calcitonin Function
Inhibits PTH action
Inhibits Vitamin D action
What conditions initiate Calcitonin secretion
high serum levels of calcium
How much of total calcium is stored in serum?
< 1.0%
45% free ionized, 40% bound to protein, 15% complexes
TOTAL Calcium Normal Ranges:
Normal Child: 8.8 – 10.8 mg/dl
Normal Adult: 8.6 – 10.0 mg/dl
Calcium Sample Requirements
Serum
Lithium heparin plasma
Clinical Significance of Calcium Serum Levels
open heart or major surgery due to role in maintaining cardiac output/BP
Calcium interfering substances
EDTA/Oxalate binds calcium
Aerobic collection decreases Calcium
Calcium Methodology
Ion Selective Electrode
Orthocresolphthalein complexone (OCPC) – Ca binds forms purple complex
Chloranilic Acid
Fluorescene
Atomic Absorption
Ionized Calcium
Neonate: 4.8 – 5.9 mg/dl
Normal Child: 4.8 – 5.5 mg/dl
Normal Adult: 4.6 – 5.3 mg/dl
24 hr Urine: 100 – 300 mg/day
Location of Phosphates in body
80% Bone
20% Soft Tissue
<1% free unbound in Serum
Phosphate Reference Ranges
Normal Neonates: 4.5 – 9.0 mg/dl
Normal Child: 4.5 – 5.5 mg/dl
Normal Adult: 2.2 – 4.5 mg/dl
Normal Urine: 0.4 – 1.3 g/day
Phosphate Specimen Requirements
Serum
Lithium heparin plasma
Phosphate Interfering Substances
Oxalate
citrate
EDTA (binds Ca+)
Hemolysis (intracellular phosphate released)
Collection time/circadian rhythm (24hr best)
Phosphate Testing Methodology
formation of ammonium phosphomolybdate complex read by specrtophotometry
Vitamin D clinical Significance
skeletal formation and mineral homeostasis
Magnesium location in body
53% Bone
46% muscle, organ, soft tissue
<1% serum)
Magnesium Reference Values
Adult Normal: 1.6 – 2.7 mg/dl
Magnesium Clinical Significance
cardiovascular metabolism neuromuscular Activator of enzymes for glycolosis ion pumps neuromuscular transmissions
Magnesium Sample Requirements
Serum
Lithium heparin plasma
24 hour urine (diurinal variation)
Magnesium Interfering Substance
Hemolysis
higher concentration do to intracellular magnesium released
Magnesium Methodology
reference: Atomic Absorption
Calmagite, formazen dye, methythymol blue
colormetric complexes/spectrophotometry
physiological formation of Vitamin D
- Diet or sunlight exposure obtains Vitamin D3 (cholecalciferol) inactive form
- Liver converts to 25-hydrozycholecalciferol inactive form (stored in liver and removed by bile excretion)
- Kidney converts 1,25-dihydroxycholecalciferol into active form
Decrease in serum calcium cause PTH production which increases the renal production of active Vita D.
Active Vitamin D increases intestinal Calcium absorption and increases PTH effect on bone resorption
Vitamin D Target Organs
Intestines: increases calcium and phosphorus absorption
Bone: enhances PTH effects of bone resorption of calcium
Kidney: promotes renal reabsorption of Calcium and Phosphorus
Function of Calcitonin
inhibit PTH action
Inhibit vitamin D action
Relationship of Calcium and Phosphorus
Calcium forms complexes with phosphates in plasma
Reciprocal of each other
Increase calcium in plasma = decreases phosphates since it binds it all
Increase Phosphates in plasma = decrease calcium since it binds it all
tissue sources of alkaline phosphatase.
4 Isoenzymes: structurally different with same job
Liver
Bone
Placenta
Intestines
Role of Alkaline Phosphatase
catalyzes hydrolysis of phosphoesters at alkaline pH to free phosphates from organic phosphate esters
Indicators of disease based on Alkaline Phos
Liver damage = higher alkaline phosphatase / liver damage = free flow of alk phos into bile and blood
Pregnancy = higher bone and placenta alkaline phosphatase levels
Crush injury = higher bone alkaline phosphatase
elevated Alkaline Phosphatase
How to determine bone or liver cause?
- measure total ALP activity
- heat sample at 56oC for 10 Minutes
- measure total ALP activity
if 20% total activity = LIVER (heat stable: liver lasts)
Majority location of Copper
90% bound with ceruloplasmin (synthesized in liver)
Causes of Deficiency in Copper
due to malnutrition
malabsorption
increased Zinc (competes for absorption)
Causes of Excess Copper
Increased injestion (copper bakeware)
Menkes Syndrome
decreased copper
Recessive x-linked genetic disorder
Mental deterioration, failure to thrive, kinky hair, early death
Wilson’s Disease
increased copper (Copper excretion impaired)
Autosomal recessive
Kayser-Fleisher rings: copper deposits in ring around iris
Treatment: Administer zinc to compete with copper
Zinc
competes with copper and iron
Fctn: growth, wound healing, reproduction, immune system (activator for 300+ enzymes)
Deficient: malabsorption, chronic liver/kidney disease, alcoholism
Maganese
transported by albumin and transferrin / associated with enzymes
Higher concentration in RBC’s (don’t want hemolysis in testing
Osteomalacia:
decreased mineralization of bone matrix
Causes: Vitamin D deficiency (serum Calcium and Phos are low)
Lab would see low serum Calcium and Phosphates
Osteoporosis
decreased bone density / skeletal fragility
