hypercalcemia
DESCRIPTION
approach and management of hypercalcemiaTRANSCRIPT
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Hypercalcemia
• Commonly encountered in Practice• Diagnosis often is made incidentally• The most common causes are primary
hyperparathyroidism and malignancy• Diagnostic work-up includes measurement of
serum calcium, intact parathyroid hormone (I-PTH), h/o any medications
• Hypercalcemic crisis is a life-threatening emergency
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Hypercalcemia
• The skeleton contains 98 percent of total body calcium; the remaining 2 percent circulates throughout the body
• One half of circulating calcium is free (ionized) calcium, the only form that has physiologic effects.
• The remainder is bound to albumin, globulin, and other inorganic molecules
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Distribution Of Calcium
CALCIUM
ECF8.5-10.6 mg/dl
2.25-2.65 mmol//l
ICFCYTOPLASMIC FREE
50-100 nmol/l
PROTEIN BOUND45%
DIFFUSIBLEULTRAFILTRABLE
55%
IONIZED45%
COMPLEXED10%90% ALBUMIN
10% GLOBULIN
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Protein binding of calcium• Influenced by pH.• Metabolic acidosis decrease protein binding
increase ionized calcium.• Metabolic alkalosis increase protein binding
decrease ionized calcium.• Fall in pH by o.1 increases serum calcium by 0.1
mmol/L• Corrected calcium = (4.0 mg/dl - [plasma
albumin]) X 0.8 + [serum calcium]
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CALCIUM PHYSIOLOGY: BLOOD CALCIUM
• Blood Calcium Is Tightly Regulated–Principle Organ Systems•Gut, Bone, Kidneys
–Hormones• Parathyroid Hormone
(PTH),calcitonin,vitamin D
– Integrated Physiology Of Organ Systems And Hormones Maintain Blood Calcium
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CALCIUM PHYSIOLOGY:BLOOD CALCIUM
• Calcium Flux Into And Out Of Blood– “In” Factors: Intestinal Absorption, Bone Resorption– “Out” Factors: Renal Excretion, Bone Formation (Ca
INCORPATION INTO BONE)–Balance Between “In” And “Out” Factors•Organ Physiology Of Gut, Bone, And Kidney•Hormone Function Of PTH And Vitmamin D
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CALCIUM HOMEOSTASIS
DIETARY CALCIUM
INTESTINAL ABSORPTIONORGAN PHYSIOLOGY
ENDOCRINE PHYSIOLOGY
DIETARY HABITS,
SUPPLEMENTSBLOOD CALCIUM
BONE
KIDNEYS
URINE
THE ONLY “IN”
THE PRINCIPLE “OUT”
ORGAN PHYS.
ENDOCRINE PHYS.
ORGAN, ENDOCRINE
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TRANSCELLULAR CALCIUM ABSORPTION
TRPV5
NUCLEUS
CCALBINDIN D9k
NCX1 PMCA1b CaSR
calcium
LUMEN
BLOOD
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Factors affecting calcium absorption in gut
• Increased • Decreased
• Vit D• Ingestion with alkali• PTH• GH• Acidic milieu
• High po4 content in diet• High veg fibre• High fat content• Corticosteroid treatment• Estrogen deficiency• Advanced age• Gastrectomy• Intestinal malabsorption
syndrome• DM• Renal failure
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RENAL HANDLING OF CALCIUM
• 8-10 g calcium filtered across the glomerulus per day.
• 200 mg = 2 % is excreted• Rest reabsorbed across renal tubules.
• PCT: 60-65%• mTALH: 20 %• DCT, CNT : 5%
PASSIVE
ACTIVE
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DISTAL TUBULE CALCIUM ABSORPTION
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KLOTHO
• Klotho is involved in the – Renal control of calcium, phosphate and vitamin D
metabolism– Suppresses phosphate re-absorption in renal
proximal tubule, by directly binding to FGF receptors
– Regulates Ca2+ re-absorption in the distal convoluted tubule by • Stabilizing the TRPV5 Ca2+ channel in the plasma
membrane
Nephrol Dial Transplant 2007; 22: 1524–1526
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KLOTHO
Inhibits renal 1-alpha 25 hydroxylase activity and thereby ►Decreases circulating calcitriol levels
– Therefore appears to ►Synergize with the renal tubular effects of parathyroid
hormone (PTH) on Ca2+ and phosphate transport, whereas ►Antagonizes the stimulatory effect of PTH on calcitriol
synthesis by the kidney
Nephrol Dial Transplant 2007; 22: 1524–1526
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PTH/Calcium HomeostasisLow circulating serum calcium
concentrations stimulate the parathyroid glands to secrete PTH, which mobilizes calcium from bones by osteoclastic stimulation.
PTH also stimulates the kidneys to reabsorb calcium and to convert 25-hydroxyvitamin D3 (produced in the liver) to the active form, 1,25-dihydroxyvitamin D3, which stimulates GI calcium absorption.
High serum calcium concentrations have a negative feedback effect on PTH secretion.
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CALCIUM, PTH, AND VITAMIN D FEEDBACK LOOPS
NORMAL BLOOD Ca
RISING BLOOD Ca
FALLING BLOOD Ca
SUPPRESS PTH
STIMULATE PTH
BONE RESORPTION
URINARY LOSS
1,25(OH)2 D PRODUCTION
BONE RESORPTION
URINARY LOSS
1,25(OH)2 D PRODUCTION
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PTH• Renal effects (steady state maintenance)– Increased reabsorption of calcium– Stimulation of 25(OH)D-1alpha-hydroxylase
• Bone effects (immediate control of blood Ca)– Causes calcium bone release within minutes– Chronic elevation increases bone remodeling and
increased osteoclast-mediated bone resorption– However, PTH administered intermittently has
been shown to increase bone formation and this is a potential therapy for osteoporosis
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FUNCTION OF VITAMIN D• Tissue Specificity– Gut
• Stimulate Transepithelial Transport Of Calcium And Phosphate In The Small Intestine (Principally Duodenum)
– Bone• Stimulate Terminal Differentiation Of Osteoclasts• Stimulate Osteoblasts To Stimulate Osteoclasts To Mobilize Calcium
– Parathyroid• Inhibit Transcription Of The PTH Gene (Feedback Regulation)
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Calcium Homeostasis
PTH• 4 PT glands• 84 AA
hormone• Low Ca
stimulates it
Calcitriol (D)• Active bone
formation• Main effect is
on the Gut• PTH Vit. D
Calcitonin• Para follicular C
of Thyroid• 34 AA
hormone• On Kidney
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FUNCTIONS
• Muscle contraction• Neuromuscular / nerve conduction• Intracellular signalling• Bone formation• Coagulation • Enzyme regulation
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Grades Of Hypercalcemia
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HypercalcemiaI.Parathyroid-related
-Primary hyperparathyroidism-Lithium therapy-Familial hypocalciuric hypercalcemia
II. Malignancy-related-Solid tumor with metastases (breast)-Solid tumor with humoral mediation of hypercalcemia (lung, kidney)-Hematologic malignancies (multiple myeloma, lymphoma, leukemia)
III. Vitamin D-related-Vitamin D intoxication-↑ 1,25(OH)2D; sarcoidosis and other granulomatous diseases-Idiopathic hypercalcemia of infancy
IV. Associated with high bone turnover-Hyperthyroidism-Immobilization-Thiazides-Vitamin A intoxication
V. Associated with renal failure-Severe secondary hyperparathyroidism-Aluminum intoxication-Milk-alkali syndrome
Primary hyperparathyroidism and cancer account for 90% of cases of hypercalcemia
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Diagnostic Approach
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Primary Hyperparathyroidism
• 50% case of hypercalcemia in general population.• Prevalence : 1 %, 2% in post menopausal women.• Peak incidence in 6th decade.• Adenoma : single enlarged parathyroid gland
responsible in 80-85% cases• Hyperplasia : in 10-15% cases. Sporadic or part of
MEN• Carcinoma : 0.05-1%
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Clinical Presentation
• 80 % cases: asymptomatic, diagnosed on routine lab finding of increased serum calcium
• 20-25% cases: chronic course with mild or intermittent hypercalcemia, recurrent renal stones, complication of nephrolithiasis
• 5-10% have severe and symptomatic hypercalcemia and overt osteitis fibrosa cystica; in these patients the parathyroid tumor is usually large (greater than 5.0 g).
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Diagnosis
The diagnosis of PHPT is established by laboratory testing showing
• hypercalcemia,• Inappropriately normal or elevated blood levels of
PTH,• Hypercalciuria, • Hypophosphatemia,• Phosphaturia,• And increased urinary excretion of cyclic adenosine
monophosphate
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Treatment
• Parathyroidectomy indicated in all symptomatic patients.
• Asymptomatic patient :
• Serum calcium > 1 mg/dl above normal, • reduced bone mass (T-score of less than –2.5 at any site), • GFR of less than 60 mL/min, or • age younger than 50 years. • Hypercalciuria (>400 mg calcium per 24 hours) is no longer
regarded as an indication for parathyroid surgery, since hypercalciuria in PHPT was not established as a risk factor for stone formation.
parathyroidectomy
If none of above things met: annual monitoring of patient for serum calcium, renal function, BMD
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Familial Hypocalciuric Hypercalcemia
• Caused by an inactivating MUTATION of calcium-sensing receptors.
• Sensitivity of receptors to calcium DECREASES, requiring higher calcium levels to suppress PTH secretion.
• Fractional excretion of calcium is lower than 1%, despite hypercalcemia.
• Hypercalcemia in FHH has a generally benign course and is resistant to medications, except for some cases successfully treated with the calcimimetic agent cinacalcet.
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Clinical (>12)1. Renal : NDI , Stone, Nephrocalcinosis2. Gi :Nausea/Vomiting, Constipation, Peptic
ulcer, Pancreatitis3. Neuro :Weakness, Drowsiness4. Cardio : Short Qt(<0.3),broad T, Heart Block,
Vent Arrhythmia, asystole5. Musculo : Cramps, Bone Pain, Pathologic Fx6. Others : Band Keratopathy
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Symptoms
• Bones, stones, abdominal groans, and psychic moans. • Malaise, fatigue, headaches, diffuse aches
and pains, constipation.• Patients are often dehydrated• Lethargy and psychosis when hypercalcemia is
severe.• Calcifications in skin, cornea, conjunctiva, and
kidneys.
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