Calcium Flashcards
What is the normal range for serum calcium?
8.5–10.5 mg/dL.
How is calcium distributed in the blood?
- 45% is bound to albumin
- 40% is ionized (physiologically active)
- 15% is bound to organic anions
Why is ionized calcium the most physiologically relevant?
Ionized calcium is hormonally regulated and directly affects neuromuscular and cardiac function.
How does serum calcium change with acidosis and alkalosis (metabolic or respiratory)?
- Acidosis will increase ionized calcium
- Alkalosis will decrease ionized calcium
What pathological states alter the serum protein levels leading to changes in calcium?
- primary hyperparathyroidism
- chronic kidney disease
- multiple myeloma (elevated proteins can increase corrected calcium)
How does serum albumin affect total calcium levels?
For every 1 g/dL decrease in albumin, the total serum calcium decreases by 0.8 mg/dL.
How do you calculate corrected calcium?
Corrected Ca (mg/dL) = (4 - Serum Albumin) x 0.8 + Measured Ca
What is the definition of hypocalcemia?
Serum calcium <8.5 mg/dL.
What are the neuromuscular signs of hypocalcemia?
- Irritability
- Tetany
- Perioral paresthesias
- Muscle cramps
- Chvostek’s sign (facial twitching)
- Trousseau’s sign (carpal spasm)
What are the cardiac signs of hypocalcemia?
Prolonged QT interval, which can progress to Torsades de Pointes.
What are the two major categories of hypocalcemia?
- Low PTH (hypoparathyroidism)
- High PTH (secondary causes)
What are the causes of hypocalcemia with low PTH?
- Post-surgical (parathyroidectomy)
- Autoimmune hypoparathyroidism
- Infiltrative diseases (hemochromatosis, Wilson’s disease, sarcoidosis).
What laboratory findings are seen in hypoparathyroidism?
- Inappropriately low to normal PTH
- Low calcium
- High phosphate
What are the causes of hypocalcemia with high PTH?
- Vitamin D deficiency
- Chronic kidney disease
- Acute pancreatitis
- Tumor lysis syndrome
- Hypomagnesemia
- Citrate from blood transfusions
- Pseudohypoparathyroidism
What is the treatment for hypocalcemia due to chronic kidney disease?
- Calcium supplementation
- Vitamin D analogs (calcitriol)
- Phosphate binders if hyperphosphatemia is present
How does acute pancreatitis cause hypocalcemia?
Pancreatic lipases release free fatty acids, which bind calcium and precipitate as soaps.
How does tumor lysis syndrome cause hypocalcemia?
Hyperphosphatemia from tumor lysis binds calcium, leading to hypocalcemia.
Why does hypomagnesemia lead to hypocalcemia?
Magnesium is necessary for PTH secretion; low Mg inhibits PTH release, leading to hypocalcemia.
How does vitamin D affect calcium levels?
- Dietary intake
- Liver metabolism
- Renal metabolism
- Modulation of PTH
How does citrate in blood transfusions cause hypocalcemia?
Citrate binds calcium, reducing ionized calcium levels and leading to symptomatic hypocalcemia.
What is the treatment for symptomatic severe hypocalcemia (Ca <7.5 mg/dL)?
Intravenous calcium gluconate is used to treat acutely symptomatic hypocalcemia (eg, oral paresthesias, carpopedal spasm, tetany, seizures).
What is the first-line treatment for severe symptomatic hypocalcemia (Ca <7.5 mg/dL or severe symptoms)?
IV calcium gluconate or calcium chloride, administered slowly to prevent cardiac arrhythmias.
What is the treatment for mild or asymptomatic hypocalcemia?
Oral calcium and vitamin D supplementation.
What are the oral medication options for moderate hypocalcemia (Ca 7.5-8.5 mg/dL, mild symptoms)?
Oral calcium supplementation (calcium carbonate or calcium citrate) with vitamin D.
Why is vitamin D supplementation necessary in hypocalcemia treatment?
Vitamin D increases intestinal calcium absorption and prevents recurrence of hypocalcemia.
What must be corrected before calcium in patients with hypocalcemia and hypomagnesemia?
Magnesium, as low Mg inhibits PTH secretion.
What should be corrected first in hypocalcemia associated with hypomagnesemia?
Magnesium must be corrected first, as low Mg inhibits PTH secretion and calcium absorption.
What is the long-term management of chronic hypoparathyroidism?
Lifelong calcium and vitamin D supplementation; recombinant PTH (teriparatide) for severe cases.
What is the management for postoperative hypocalcemia following parathyroidectomy?
Monitor calcium levels closely; provide oral calcium and vitamin D to prevent ‘hungry bone syndrome’.
What is the definition of hypercalcemia?
Serum calcium >10.5 mg/dL.
What are the major causes of hypercalcemia?
- Primary hyperparathyroidism
- Malignancy
- Vitamin D toxicity
- Granulomatous diseases
- Thiazide diuretics
- Lithium
- Immobilization
- Familial hypocalciuric hypercalcemia (FHH)
What are the lab values for primary hyperparathyroidism?
Elevated calcium, low phosphate, high PTH, usually due to a parathyroid adenoma.
How is hypercalcemia due to primary hyperparathyroidism managed?
Parathyroidectomy if symptomatic or if calcium >11.5 mg/dL, osteoporosis, or renal involvement.
What is the pharmacologic treatment for hypercalcemia in patients who are not surgical candidates?
Cinacalcet, a calcimimetic that reduces PTH secretion.
How does secondary hyperparathyroidism present?
Low calcium, high PTH, seen in chronic kidney disease or vitamin D deficiency.
How does tertiary hyperparathyroidism present?
- High calcium
- High PTH
- Normal or high phosphate due to long-term CKD and parathyroid hyperplasia.
What differentiates familial hypocalciuric hypercalcemia (FHH) from primary hyperparathyroidism?
FHH has high serum calcium, high PTH, but low urinary calcium (<100 mg/24hr), while primary hyperparathyroidism has high urinary calcium.
What is the treatment for familial hypocalciuric hypercalcemia (FHH)?
No treatment is needed as this is a benign, autosomal dominant condition.
What malignancies commonly cause hypercalcemia?
- Squamous cell carcinoma (lung, head & neck) via PTHrP
- Breast cancer (bone metastases)
- Multiple myeloma
- Renal cell carcinoma
- Lymphomas (vitamin D overproduction)
- These tend to present with elevated calcium, low phosphate (the renal function is usually un impaired and allows for excretion of phosphate), and low PTH.
What medications tend to cause hypercalcemia?
- Milk alkali syndrome
- Vitamin D Hypervitaminosis
- Lithium
- Hydrochlorothiazide
What is the treatment approach for hypercalcemia secondary to lithium use?
Discontinue lithium if possible; if not, consider cinacalcet to reduce PTH secretion.
What is the treatment for milk-alkali syndrome?
Discontinue calcium-containing supplements and provide IV hydration to restore kidney function.
How is hypercalcemia due to vitamin D toxicity managed?
Discontinue vitamin D supplements, provide IV fluids, and consider glucocorticoids to reduce vitamin D activation.
What is the acute management of severe hypercalcemia (>14 mg/dL)?
- IV normal saline
- Calcitonin
- Bisphosphonates for long-term management
When are bisphosphonates used in hypercalcemia?
For long-term control, especially in malignancy-associated hypercalcemia.
How is hypercalcemia due to prolonged immobilization managed?
Bisphosphonates and early mobilization to reduce bone resorption.
What medication is used for long-term management of hypercalcemia in malignancy?
Bisphosphonates (e.g., zoledronic acid, pamidronate) inhibit bone resorption and prevent recurrent hypercalcemia.
When should dialysis be considered in hypercalcemia?
In cases of severe hypercalcemia with kidney failure.
What is the role of glucocorticoids in hypercalcemia?
Used in hypercalcemia due to lymphoma, multiple myeloma, or granulomatous diseases.
What is the initial treatment for severe hypercalcemia (>14 mg/dL) or symptomatic patients?
IV normal saline hydration to enhance renal calcium excretion, followed by calcitonin for rapid reduction.
What is the emergency management for hypercalcemic crisis (Ca >18 mg/dL)?
Aggressive IV hydration, calcitonin for rapid effect, bisphosphonates, and hemodialysis if refractory.
What is the treatment for hypercalcemia due to granulomatous diseases or lymphoma?
Glucocorticoids (e.g., prednisone) reduce vitamin D production and calcium absorption.
When is dialysis indicated for hypercalcemia?
In patients with kidney failure, refractory hypercalcemia, or life-threatening calcium levels.
What is the role of loop diuretics in hypercalcemia treatment?
Furosemide can be used after volume resuscitation to promote calcium excretion but should not be used as initial therapy.
