IM Endo Calcium Bone USMLE 2
Terms
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Definition:
Disease of impaired bone mineralization -
Osteomalacia
(Mineralization = Malacia) - Osteomalacia in children
- Rickets
-
Basic etiology of Osteomalacia
(4) -
Decreased Calcium absorption;
Dietary Calcium deficiency;
Vitamin D deficiency;
Hypophosphatemia -
Causes of dietary Calcium deficiency
(3)* -
Malabsorption syndromes;
Gastrectomy;
Dumping syndrome -
Main Causes of Vitamin D deficiency
(2) -
Hepatobiliary and Pancreatic diseases
(loss of bile acids or pancreatic lipase reduce absorption of fat-soluble vitamins);
Renal Osteodystrophy -
Causes of Hypophosphatemia
(2) -
Renal Tubular Acidosis;
Falconi's syndrome -
Dx:
Bone pain, weakness, difficulty walking: broad-based waddling gait w/ short strides; thoracic kyphosis -
Osteomalacia
(Rickets in children) -
What do blood tests show to Dx Osteomalacia?
(3) -
Labs:
1. Low - nml Calcium;
2. Low - nml Phosphate;
3. High Alk-phos
(possible high PTH) -
Tx for Osteomalacia
(2) -
Tx underlying disorder;
Calcium and Vitamin D supplements -
Definition:
Systemic disorder resulting in a reduction of bone mass that leads to increased risk of fracture - Osteoporosis
-
Risk factors for Osteoporosis
(6) -
Elderly Female;
Post-menopause;
Family Hx;
Smoking;
Thin body;
Sedentary lifestyle - Pathophysiology of Osteoporosis
- Reduction of bone mass occurs due to an imbalance b/t bone aquisition and bone reabsorption; w/o change in the ratio of mineral to organic bone
- Histology of Osteoporosis
-
Decreased cortical thickness and number (and size) of cancellous bone trabeculae
(especially horizontal) -
When does osteoporosis usually become symptomatic?
(2) types -
when Fracture occurs:
Vertebral body fracture;
Hip fracture - Dx lab blood test results for Osteoporosis
-
Everything is normal:
Serum Ca++ and PO4- are usu normal;
Alk-phos is normal unless there is a fracture, then it's increased -
How is bone mineral density measured?
(2) Dx results -
Dual X-ray Absorptiometry (DEXA) scan
T-score < -2.5 = Osteoporosis
T-score -2.5 to -1 = Osteopenia -
Differential in Osteoporosis
(4)* -
Malignancy;
Hyperparathyriodism;
Osteomalacia;
Padget's disease of the bone -
Prevention and Tx for Osteoporosis
(4) -
Dietary Calcium and Weight-bearing exercises;
Estrogen replacement therapy;
Calcitonin;
Bisphosphonates (Alendronate) w/ Vitamin D and Calcium supplements -
Definition:
Chronic Dz of adult bone in which localized areas of bone becomes hyperactive, and the normal bone matrix is replaced by softened and enlarged bone - Padget's Disease of the bone
-
If Alkaline Phos is elevated, what is the next step?
(2) -
Send GGT to determine if it is Hepatic (elevated GGT) or bone (not elevated)
or
Check to see if it is heat-labile (Bone), where hepatic is not -
Histology:
Hyperactive bone turnover w/ enlarged multinucleated osteoclasts - Padgets Disease of the bone
-
Dx:
45-yo male is found to have an elevated alkaline phosphatase during a routine blood test. No other abnormalities were found. Further workup reveals the enzyme to be heat labile - Padget's Disease of the bone
-
Radiologic finding:
area of hyperlucency of the bone surrounded by a hyperdense border - Padget's Disease of the bone
-
Tx for Padget's Disease of the Bone for:
1. Pain relief
2. Anatomic deformity or impingement
3. to Decrease bone reabsorption
4. to assist w/ cardiac failure or neurologic deficits -
1. Pain = Indomethacin
2. Deformity = Osteotomy of the bone
3. Decrease Reabsorption = Bisphosphonates
4. Assist in CardiacNeuro = Calcitonin - What is the Normal serum Calcium range?
- 8.5 - 10.2 mg/dL
-
Etiology of Hypocalcemia
(8)* -
IV STRAP:
Insufficient PTH;
Vitamin D deficiency;
Sepsis / Severe Mg deficiency;
Toxins;
Rhabdomyolysis;
Albright's Osteodystrophy (Pseudohypoparathyroidism);
Pancreatitis -
Osteoporosis Risk factors
(8)* -
FACELESS:
Family history;
Alcohol;
Corticosteroids;
Elderly Female;
Low Calcium;
Estrogen low (Menopause);
Smoking;
Sedentary lifestyle -
First sign/Sx of Hypocalcemia
Name and describe (2) other common signs seen in PE -
first sign:
Circumoral Paresthesia
Chvostek's sign:
Facial muscle spasm w/ tapping of the facial nerve
Trousseau's sign:
Carpal spasm after occluding blood flow in forearm w/ BP cuff - What is seen w/ EKG for Hypocalcemia?
-
Prolonged QT and ST intervals
(also peaked T-waves can be seen as in HyperK) - How can Calcium correct for Hypoalbuminemia?
- Adjust Calcium upward by 0.8mg/dL for each 1.0g/dL of albumin below normal
-
Toxins that cause low calcium
(5)* -
Can Produce A Calcium Fall:
Cimetidine;
Phenytoin;
Alcohol;
Citrate;
Fluoride -
Etiology of Hypercalcemia
(14)* -
CHIMPANZEES:
Calcium supplementation;
Hyperparathyroidism / Hyperthyroidism;
Immobility;
Meds / Multiple Myeloma;
Padget's Dz;
Addison's Dz / Acromegaly;
Neoplasm metastasis;
Zollinger-Ellison syndrome;
Excess Vit-A;
Excess Vit-D;
Sarcoidosis or TB (granulomatous dz) -
MCC of hypercalcemia
MCC for inpatient? -
Primary Hyperparathyroidism
Inpatient: Malignancy -
Dx:
malaise, HA, diffuse aches, dehydration, N/V, nodules on skin, cornea, conjunctiva and kidneys -
Hypercalcemia
(nodules are calcifications) -
Drugs that cause Hypercalcemia
(5)* -
C-TALE:
Calcium supplementation;
Thiazides;
Antacid abuse;
Lithium;
Excess Vitamin D -
Dx:
"Stones, bones, groans and psychiatric overtones" - Hyperparathyroidism
-
Tx for Primary Hyperparathyroidism patient w/ underlying cardiac failure
(drug and maintenance) -
Lasix to maintain diuresis
and
Pulmonary artery pressure monitoring to avoid volume overload - Pathophysiology behind Renal Osteodystrophy
-
Nephron loss reduces phosphate excretion, causing hyperphosphatemia, which lowers serum calcium and increases PTH secretion
(secondary parahyperthyroidism) - (3) Bone lesions assoc w/ Secondary Hyperparathyroidism
-
Osteitis Fibrosa Cystica;
Adynamic Bone Dz;
Osteomalacia -
Definition:
Normal bone is replaced by fibrous tissue, primitive woven bone and cysts - Osteitis Fibrosa Cystica
-
Dx:
bone pain, proximal muscle weakness, pruritis, soft-tissue ulcerations, diffuse soft-tissue calcifications -
Secondary Hyperparathyroidism
(Renal Osteodystrophy) -
Goal and Tx for Secondary Hyperparathyroidism /
Renal Osteodystrophy
(2 drugs and 2 if drugs dont work) -
Goal:
Normalize calcium-phos balance
Tx:
1. Aluminum-containing antacids: reduce GI absorpt of PO4-
2. Vit-D w/ Calcitrol: inc serum Ca++ and reverse bone damage
3. Subtotal parathyroidectomy
4. Renal transplant - If patient has hypocalemia or hypophosphatemia (or both) what is the next step?
-
Check for Hypomagnesemia:
Ca++ and PO4- will not elevate if Magnesium is low -
Dx:
Rapid transfer of Calcium into bones following removal of hyperactive parathyroid
What electolyte disorder can it cause? -
Hungry Bone syndrome
can cause: Hypomagnesemia