seminar on calcium
TRANSCRIPT
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Dr. IFTHAQAR. H. F
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CALCIUM METABOLISM
Dr. IFTHAQAR. H. F
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INTRODUCTION
Calcium is the most abundant mineral in the body.
The body of a young adult human contains about
1100 g (27.5 mol) of calcium.
Normal levels ranges from 8.5 to 10.5 mg/dl
About 99% of body calcium is in the form of
hydroxyapatite crystal in the bone.
1% in ECF, ICF .
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THE 1% CALCIUM
In blood, calcium is found in 3 forms:
Ionised (biologically active) 50%
Bound to proteins 40% &
as Complexes with substances(anions) such as
HCO3, citrate, etc.. 10%
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DISTRIBUTION OF CALCIUM
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WE ARE INTERESTED IN IONIZED CALCIUM
LEVELS: WHY??BECAUSE,
Calcium messenger system – regulates cell
function.
Activates cellular enzyme cascades.
Muscle contraction.
Nerve impulse conduction.
Blood coagulation.
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CALCIUM ABSORPTION (DRAW)
Ca2+ is transported across the brush border of
intestinal epithelial cells via channels – TRPV6
Binds to intracellular protein known as calbindin-
D9k
Transported into the bloodstream by either a
sodium/calcium exchanger (NCX1) or a calcium-
dependent ATPase.
The overall transport process is regulated by 1,25-
dihydroxycholecalciferol
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CALCIUM EXCRETION
Plasma Ca2+ is filtered in the kidneys.
98–99% of the filtered Ca2+ is reabsorbed.
(proximal(60%), loop of henle & distal-40%)
Distal tubular reabsorption depends on the TRPV5
channel. – controlled by PTH
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CALCIUM HOMEOSTASIS
Three hormones
–PTH
–1,25 (OH)2 CC
–Calcitonin
Three target organs
–Bone
–Gut
–Kidney
Three bone cells
–Osteoblasts
–Osteocytes
–Osteoclasts
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Hormone Effect on bones Effect on gut Effect on
kidneys
Parathyroid
hormone
increase Ca++,
decrease PO4
levels in blood
Supports
osteoclast
resorption
Indirect effects via
increase calcitriol
from 1-
hydroxylation
Supports Ca++
resorption and
PO4 excretion,
activates 1-
hydroxylation
Calcitriol
(vitamin D)
Ca++, PO4 levels
increases in
blood
No direct effects
Supports
osteoblasts
Increases Ca++
and PO4
absorption
No direct effects
Calcitonin
causes Ca++,
PO4 levels
decrease in blood
when
hypercalcemia is
present
Inhibits osteoclast
resorption
No direct effects Promotes Ca++
and PO4 excretion
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CALCIUM, PTH, AND VITAMIN D
FEEDBACK LOOPS
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CALCIUM LEVELS ARE AFFECTED BY:
Albumin
Blood pH
Serum phosphate
Serum magnesium
Serum bicarbonate
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HYPOCALCEMIA
Dr. IFTHAQAR. H. F
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Hypocalcemia is defined as a total serum calcium
concentration of
less than 2.1 mmol/L (8.5 mg/dL) in children,
less than 2 mmol/L (8 mg/dL) in term neonates,
less than 1.75 mmol/L (7 mg/dL) in preterm
neonates.
Hypocalcemia can present as an asymptomatic
laboratory finding
or
as a severe, life-threatening condition.
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CAUSES OF HYPOCALCEMIA
Neonatal hypocalcemia:
Early neonatal hypocalcemia (48-72 hours)
Prematurity
Poor intake, hypoalbuminemia, reduced responsiveness to vitamin D
Birth asphyxia
Delay feeding, increased calcitonin, endogenous phosphate load high, alkali therapy
Infant to diabetic mother
Magnesium depletion → functional hypoparathyroidism → hypocalcemia
IUGR
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Late neonatal hypocalcemia
Exogenous phosphate load
Phosphate-rich formulas / cow’s milk
Magnesium deficiency
Transient hypoparathyroidism of newborn
Congenital Hypoparathyroidism
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CAUSES OF HYPOCALCEMIA
In childhood:
Vitamin D deficiency.
Hypoparathyroidism.
PTH resistance – Pseudohypoparathyroidism.
Autoimmune parathyroiditis
Mitochondrial DNA mutations.
Hypomagnesaemia
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OTHER CAUSES
Malabsorption syndromes.
Hyperphosphatemia.
Alkalosis.
Pancreatitis.
Pseudohypocalcemia (ie, hypoalbuminemia)
Hungry bones syndrome
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SYMPTOMS AND SIGNS OF HYPOCALCEMIA
Neuromuscular irritability
Paresthesias
Laryngospasm / Bronchospasm
Tetany
Seizures (focal, petit mal, grand mal)
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Muscle cramps
Muscle weakness
Chvostek sign
Trousseau sign
Prolonged QT interval(>0.4sec) on ECG
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Tetany is not caused by increased excitability of the
muscles.
Muscle excitability is depressed
hypocalcemia delays ACh release at NM junctions
However, the increase in neuronal excitability
overrides the inhibition of muscle contraction.
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HISTORY THAT SUGGESTS HYPOCALCEMIA
Newborns (can be unspecific) Asymptomatic
Lethargy
Poor feeding
Vomiting
Abdominal distention
Children Seizures
Twitching
Tingling & numbness of fingers
Cramping
Laryngospasm
APROACH
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WORKUP - BLOOD
Total and ionized serum calcium levels
Serum magnesium levels
Phosphorus levels.
Parathormone levels. (PTH challenge)
Serum electrolyte and glucose levels
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Vitamin D metabolite (25-hydroxyvitamin D and
1,25-dihydroxyvitamin D) levels
Serum alkaline phosphatase levels
Urine calcium, magnesium, phosphorus, and
creatinine levels
RFT
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WORKUP - IMAGING
Chest X Ray.
Ankle and wrist X Ray.
Other:
ECG
Malabsorption workup
Karyotyping (22q11 & 10p13 deletion)
Family screening
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MANAGEMENT
1. Dependent on the underlying cause and
severity
2. Administration of calcium alone is only
transiently effective
3. Mild asymptomatic cases: Often adequate to
increase dietary calcium by 1000 mg/day
4. Symptomatic: Treat immediately
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TREATMENT OF HYPOCALCAEMIASymptomatic hypocalcaemia
IV Calcium should only be given with close monitoring
Should be on cardiac monitor.
Dose: Cal gluconate (10mg/kg -1ml/kg of 10% solt)
Mix with NaCl or 5 % D/W (not bicarbonate/lactate containing
solutions)
Risks
Tissue necrosis/calcification if extravasates
Calcium can inhibit sinus node bradycardia + arrest
Stop infusion if bradycardia develops
Avoid complete correction of hypocalcaemia
With acidosis and S-Ca – give Ca before correcting
acidosis [Acidemia increases the ionized calcium levels by
displacing calcium from albumin. If acidemia is corrected
first, ionized calcium levels decrease]
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If Mg is cause of S-Ca – treat and correct
hypomagnesaemia
Oral supplementation 50 mg/kg/day of
elemental Ca
Cal carbonate is best as it contains 40% of
elemental cal.
Most cases require Vit D supplementation.
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HYPERCALCEMIA
Dr. IFTHAQAR. H. F
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Hypercalcemia is defined as total serum calcium >
10.5 mg/dl(>2.6 m mol/L ) or ionized serum
calcium > 5.6 mg/dl ( >1.4 m mol/L )
Severe hypercalemia is defined as total serum
calcium > 14 mg/dl (> 3.5 mmol/L)
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PATHOPHYSIOLOGY:
Hypercalcemia is caused by
Increased bone resorption,
increased gastrointestinal absorption of calcium,
and
decreased renal excretion of calcium
Hypercalcemia leads to hyperpolarization of cell
membranes.
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CAUSES OF HYPERCALCEMIA:
1. Parathyroid hormone (PTH) excess. - HPTH
2. Parathyroid Hormone–related Peptide (Pthrp)
Excess
Seen in malignancies.
3. Ca2+-sensing Receptor Inactivating Mutation.
1. Familial Hypocalciuric Hypercalcemia(FHH)
2. Neonatal Severe Hyperparathyroidism.
4. Activating Mutation of PTH/PTHrP Receptor.
5. Inactivating Mutation of PTH/PTHrP Receptor.
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6. VITAMIN D EXCESS
1. Iatrogenic
2. Ectopic production
3. Sarcoidosis, tuberculosis, granulomatous lesions,
subcutaneous fat necrosis
4. Excessively fortified milk
7. OTHER:
1. Prolonged Immobilization
2. Thyrotoxicosis
3. Hypervitaminosis A
4. Leukemia
5. Hypophosphatasia.
6. Williams Syndrome.
7. Drugs – esp, thiazide, TPN, theophyllin, lithium.
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CLINICAL MANIFESTATIONS:
HISTORY:
muscular weakness,
fatigue,
headache, anorexia,
abdominal pain,
nausea, vomiting,
constipation,
polydipsia, polyuria,
loss of weight, and fever
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SAYING:
“painful bones, renal stones, abdominal groans, psychic
moans, and neuropsychiatric
overtones”
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APPROACH TO A CHILD WITH
HYPERCALCEMIA:
Evaluation of a patient with hypercalcemia
should include a careful history and
physical examination focusing on
clinical manifestations of hypercalcemia,
risk factors for malignancy,
causative medications, and
family history of hypercalcemia
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LABORATORY TEST
Serum calcium & Ionized calcium
PTH (intact)
Serum phosphate
1,25-dihydroxyvitamin D
Alkaline phosphatase
Urine calcium
Urine Ca/Cr ratio
ECG
Shortened QT interval
Bradycardia
Widened T wave
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Primary hyperparathyroidism : PTH↑
MALIGNANCY :
1.solid tumors(humoral hypercalcemia) :PTHrP↑ ,
PTH↓
2.Multiple myeloma and breast cancer(osteolytic
hypercalcemia ) : alkaline phosphatase ↑, PTH↓
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Granulomatous(sarcoidosis, tuberculosis,
Hodgkin's lymphoma) :
calcitriol (1,25-OH vitamin D3 ) ↑, PTH↓
Familial hypocalciuric hypercalcemia :
24-hour urinary calcium ↓, PTH ↑
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IMAGING STUDIES
Plain X-ray
demineralization, pathologic fractures, bone cysts, and
bony metastases.
Renal imaging:
calcifications or stones
USG of the parathyroid glands:
hyperplasia or adenoma
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MANAGEMENT:
Medical:
Initial treatment involves hydration to improve
urinary calcium output. (Normal saline)
Loop diuretic is also added. (Furosemide)
Bisphosphonates serve to block bone resorption
over the next 24-48 hours.
Etidronate
Clodronate
Pamidronate
Alendronate
Inhibits osteoclast action and bone resporption
Indication: hypercalcemia of malignancy
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• Calcitonin :
inhibition bone resorption and increases renal calcium excretion
4 to 8 IU per kg IM or SQ every 6 hours for 24 hours
Plicamycin (Mitharmycin) :
decreases bone resorption
25 mcg per kg per day IV over 6 hours for 3 to 8 doses
Gallium nitrate :
inhibition bone resorption
100 to 200 mg per m2 IV over 24 hours for 5 days
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Glucocorticoids :
Inhibits vitamin D conversionto calcitriol
Hydrocortisone, 200 mg IV daily for 3 days
Hemodialysis :
used in patients with renal failure
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Surgery:Patients with primary HPTH
Criteria for Surgery in Primary Hyperparathyroidism
Serum total calcium level > 12 mg per dL (3 mmol per L) at any time
Hyperparathyroid crisis (discrete episode of life-threatening hypercalcemia)
Marked hypercalciuria (urinary calcium excretion more than 400 mg per day)
Nephrolithiasis
Impaired renal function
Osteitis fibrosa cystica.
Reduced cortical bone density
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REFERENCE:
1. Ganong’s Review of Medical Physiology – 24th Ed.
2. Nelson text book of pediatrics 19th edition.
3. Hypocalcemia: Diagnosis and Treatment, Uptodate: Updated 1 October 2011
4. Pediatric Hypocalcemia, Author: Sunil Sinha, MD; Chief Editor: Stephen Kemp, MD, PhD - emedicine
5. A Practical Approach to Hypercalcemia, American Family Physician. 2003 May 1;67(9):1959-1966
6. Pediatric Hypercalcemia, Author: Ilene A Claudius, MD; Chief Editor: Stephen Kemp, MD, PhD – emedicine
7. Google search - images
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