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Bone and Mineral Disorders


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Physiological fuctions of bone
Ridged Support- kyphoscoliosis vs lowerdosis.

Role in locomotion-bipedal motion, points of attachment and leverage for muscles.

Ion Reservoir-Ca, Mg, PO stored in bone, tapped when bodies needs not met.
structure of bone
strong for weight bearing not brittle. lightweight but stiff for locomotion. dynamic architechture for growth, remodleing, repair. Protein matrix-Osteoid. Collogen I, hydroxapetate crystals-Ca,

corical bone-compact bone-long bones, structure

trabecular bone-spongy mesh, vertebra
Bone Cells
Osteoblasts-build bone, respond to PTH and VitD (VDR) lay down collegen

Osteoclasts-catabolis bone, mineral RA, stimulate by mCSF, PTH, VitD.

Osteocytes- paly a role in bone maintenance, form syncytia, communication between corical bone and bone surface.
Signs of Hypercalcemia
CNS: depression, fatigue, stupor, coma, wuscle weakness,

CV, HTN, bradycardia, short QT interval on ECG

puritis, polyuria, polydipsia, thirst, renal stone, urinary concentrating defects, dehydration

anorecia, nausea, vomiting, constipation, band keratopathy
Signs of hypocalcemia
tetany, muscle cramping, paresthesias, laryngospasm, seizures, altered mental state
coma, muscle weakness, fatigue, basil gang, brain califications

papilledema, cataracts

Lab Dx hypercalcemia
iCa and serum albumin
PTH, PTHrP, 25OH-D, 1-25 dihydrozy D, eelctrolyes, PO, Alk PO, thyrotropin, Urine Ca and creatinine
DDx Hypercalcalcemia
1. HPTH--sporadic, MEN1 or 2
2. Variant of HPTH-familial benign hypercalcemia.
3. Cancer-PTHrP tumors,
4. osteolysis
5.Granulomatous disease sarcodosis
6. Renal failure, Drugs
Primary vs Secondary Hyperparathyroidism
inpatient 90% malignancy
outpatinet 90% Primary hyperparathyriodism
Primary vs Secondary Hypoparathyroidism
1: post surgery, for thyroid/parathyroid, autoimmune of PTH gland, activating mutation of CaRs in parathyroid glands and kidney.

2. other mechanisms
Causes of Vit D deficiency
1. subclinical malabsorption, postgasterctomy state, cholestatic liver, panc disease.
2. diet is low in dairy
3. lack of sunlight exposure
4. drugs enhance clearance of 25-D
5. renal function declines gradually with age
hihg alkaline PO is indicative of osteomalacia, deminerilzation of bone.

Vit D deficiency reduces serum Ca and PO, new bone is underminerilized. disease is osteomalacia.

bone pain, waddling gait, proximal myopathy. Pseduofractions loosers zones, radiolucent bands on bony surfaces. occur at sites of nutreint arterys on done.

High bone turnover, unminerialized bone
growing bony skeleton, Kids

delayed growth, epiphyses, a variety of bony abnormalities. Rachitic rosary, ribs , bowlegged, knock knee. cupping and thinkening of the ephysial growth plates, cortical thinning.
Lab features: Primary Hyperparathyroidism
high Ca
low PO or nl
High PTH
high 25 OH-D or nl
Lab features: Humoral Hypercalcemia of maligancy
high Ca
very low PO
low 25 OH-D or nl
Lab features: Vitamin D deficiency
low Ca
nl MG
low PO or nl
very high PTH
low 25 OH-D
nl creatinine
nl 1,25 OH-d or nl
Lab Features: PTH resistance
low Ca
nl MG
high PO or nl
high PTH
nl 25 OH-D
nl creatinine
nl 1,25 OH-d or decreased
DDx of Hypomagnesemia
excessive loss: EtOH, osmotic diuresis, diuretics, antibotics, drugs, renal tubular wasting

Excessive gastrointestinal loss of Mg: Vomiting, Nasogastric suction, diarrhea, Gastroenterities, Short bowl syndrome, fistulas, malabosorption, malnutrition

pancreatitis, primary hyperaldosteronism, diabetes mellitus
Lab features: Hypomagnesemia
slighty low Ca
low MG
nl PO
nl, low, slighty, low PTH
nl 25 OH-D
nl creatinine
deacread 1,25 OH-d
Pathophysiology of hypomagnesemia
common cause of mild hypocalcemia


Mg cofactor adenyl cyclase, activated to PTHR stim. No MG, No AC, NO PTHR stim, hypoparathyroidism, hypocalciemia. insuffienct production of 1,25 OH-d
Treat Hypercalcemia
1. underlying cause
2. surigal removal parathyroid
3. glucocorticoids antagonize VD
4. rehydrate with saline
5. use loop diuretics-calcinerisis
6. block bone resorption
7. calcintonin injections
Treat Hypocalcemia
1. oral calcium supplments
2. vitamin D metabolite
3. acute-IV Cal-gluconate, IV constant infusion, only if tetany, laryngospasm, bronchospasm
Managment of Osteoporosis
PTH injections-stim bone formation
excercise, stop smoking,
ca supplimentation, vitamin D
Mx of Action:analogs of pryophosphate-inhibits osteroclast function and bone resorption. mimics of hydroxyapatite. osteoclasts senstive then other cells.

alendronate-osteoporosis. fractures decrease,
Parathyroid Hormone Injections
for osteoporisis. only true anabolic for bone. Stimulated osteoblast bone formation.

in 21 mo trail..decreased incidence of vertebral fractures.
for osteoporosis, cannot use orally,

sometimes for hypercaliciemia

inhibits osteoclast actions.

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