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34 Cards in this Set
- Front
- Back
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What percentage of calcium is stored in the bones?
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99%
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How does calcitonin work?
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Reduces calcium levels by inhibiting osteoclast bone resorption and renal tubular reabsorption of calcium
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What are the three main hormones that contribute to calcium regulation?
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1. Parathyroid hormone
2. 1, 25-dihydroxyvitamin D3 (1,25(OH)2 D) 3. Calcitonin |
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Where is Vit D synthesized?
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In the skin via UV radiation
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How is Vit D activated?
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Vit D ----liver----> 25-hydroxyvitamin D3 (25OH D)
----kidney----> 1,25 dihydroxyvitamin D3 (1,25 OH2 D, the active form) |
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What is the half-life of 1,25OH2 D?
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very short
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What is evaluated to look for 1,25OH2 D deficiency?
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Levels of 25OH D
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Where does activated vitamin D act in the cell?
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in the nucleus --> affects gene transcription
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What are the two effects that activated Vit D has on serum calcium?
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1. Increased Ca and Phosphate mobilization from the bone
2. Increased Ca and Phosphorus absorption from the GI tract. NET EFFECT of 1,25(OH)2 D = increased serum Ca, Phos |
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What is the mechanism of action of PTH?
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1. Increased osteoclast activity = serum Ca up
Increased phos reabsorption from bone = serum Phos up 2. PTH increases the 1-alpha hydroxylation of vit D at the kidney to produce active vitamin D --> this in turn increases the absorption of Ca from the gut 3. PTH increases Ca reabsorption at the kidney 4. PTH increases Phos EXCRETION by the kidney NET effect of PTH = serum Ca UP, serum phosphate DOWN |
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Normal range for serum calcium?
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8.5 - 10.5 mg/dL
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Total serum calcium measures both what and what?
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Both protein bound and unbound calcium.
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If a patient has a low serum protein, how will this affect the calcium level?
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The calcium level may be low
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How do you make adjustments for albumin and calcium? What's the formula?
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Corrected Serum Ca (mg/dL) =
(4.0 - Albumin) * 0.8 + Measured Ca For each 1 g/dL decrease in albumin, the total calcium measurement will decrease by 0.8 mg/dL |
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What two diseases account for over 90% of hypercalcemia?
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Hyperparathyroidism and malignancy
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Hyperparathyroidism: significant lab values
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PTH up, Ca up, Phos down
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Hyperparathyroidism: possible clinical findings
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Osteoporosis, kidney stones, decreased kidney function
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Describe the procedure of surgical treatment for 4 gland parathyroid hyperplasia
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total resection of 3 glands + partial removal of 4th gland.
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What are some of the reasons hypercalcemia is seen with malignancy? (4)
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1. Direct effect from bony metastises
2. Paraneoplasms secreting PTH-like hormone. Measure PTH-rp (PTH related peptide) 3. Multiple myeloma releases cytokines that activate osteoclasts. 4. Lymphoma causes an increase in 1,25 OH vitamin D in mononuclear cells |
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What are two drugs that can cause hypercalcemia?
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Lithium
Thiazide diuretics |
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When do you treat hypercalcemia regardless of symptoms?
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When serum Ca is >14 mg/dL
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Hypercalcemia: treatments
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1. Saline hydration +/- loop diuretics
2. Bisphosphonates (esp for etiologies that cause increased bone resorption) 3. Calcitonin 4. Glucocorticoids (useful for etiologies that cause overproduction of 1,25 (OH)2 vit D 5. Low Ca diet 6. Dialysis |
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Chvostek's Sign
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tap facial nerve anterior to ear --> contraction of ipsilateral facial muscle.
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Trousseau's Sign
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Inflate BP cuff at a point greater than the systolic blood pressure and hold it there for three minutes. In the absence of blood flow, the patient's hypocalcemia will cause spasm of the hand and forearm muscles (obstetrician's hand)
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Hypocalcemia: psychiatric signs
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Depression
Fatigue Anxiety |
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Hypocalcemia: CV symptoms
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bradycardia, arrhythmias, long QT
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Hypocalcemia: neuroirritability causes what?
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Tetany (cramping & paresthesias <--> laryngospasm & seizures)
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Hypocalcemia: chronic symptoms
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Skin changes: dry, puffy, coarse
Hair: brittle, coarse Nails: brittle |
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Hypocalcemia: etiologies
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Parathyroidectomy
Vitamin D deficiency (children --> rickets, adults --> osteomalacia) Magnesium deficiency --> PTH resistance --> Ca down Renal failure Excess bisphosphonates |
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Hypocalcemia: treatment
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1. IV calcium (reserve for patients with Ca below 7.5)
2. IV/PO Magnesium 3. Oral calcium (calcium carbonate) 4. Vitamin D 5. 1,25 OH)2 D (calcitrol), monitor for hypercalcemia |
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Vitamin D2
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Ergocalciferol
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Vitamin D3
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Cholecalciferol
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Hypoparathyroidism: treatment
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Most people need lifelong calcium or calcitrol
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If you lack PTH, then you will have more or less Ca in your urine?
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More.
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