Hypocalcemia & hypoparathyroidism

Question 1

What is hypocalcemia?

Answer 1

• serum calcium < 8.8 mg/dL with normal albumin

- ionized calcium < 4.45mg/dL

Question 2

What are the causes of hypocalcemia post-op?

Answer 2

• injury to parathyroid gland or its blood supply

- resection of parathyroid gland

Question 3

What are the clinical features of hypocalcemia?

Answer 3

• paresthesia
• tetany
• seizures
• muscle cramps
• muscle weakness
• confusion
• disorientation
• Chvostek’s sign
• Trousseau’s sign

Question 4

How do u calculate the correction of calcium?

Answer 4

correct calcium = 0.8 x (normal albumin - patient’s albumin) + serum calcium

normal albumin = 3.4 - 5.4

Question 5

When should a cAMP workup be ordered in hypocalcemia?

Answer 5

to differentiate between hypoparathyroidism & pseudo hypothyroidism
- elevated in hypoparathyroidism in response to PTH test

Question 6

What will be seen on an ECG in case of hypocalcemia?

Answer 6

prolonged QT secondary to hypocalcemia -> ventricular arrhythmias

Question 7

How is hypocalcemia treated?

Answer 7

• maintain serum calcium in low normal range
  mild to moderate
• oral calcium supplement (1-3g in 3 to 4 divided doses with meals) & vitamin D (calcitriol 0.5 twice a day)
• calcium carbonate (40% elemental calcium)
• calcium lactate (13%), calcium citrate (21%), calcium gluconate (9%)
• patients with PPI or elderly -> calcium citrate

Question 8

What increases the intestinal absorption of calcium?

Answer 8

Calcitriol
- short half-life -> 5 to 8 hours

Vitamin D3 (cholecalciferol) 
- longer half-life -> weeks to months 

increases phosphate absorption
- incase of severe hyperphosphatemia with vitamin D therapy -> give phosphate binders

Question 9

What is the recommended magnesium replacement for low magnesium levels?

Answer 9

• magnesium oxide 400mg BID -> could enhance calcemic recovery

Question 10

How is severe hypocalcemia treated?

Answer 10

< 7.5 &/or severe symptoms

• IV calcium
• bolus -> 1 - 2g of calcium gluconate infused over 20 mins
• calcium drip of 11g calcium gluconate in 1L 5% dextrose -> administered at 50mL/hr (IN PERSISTENT HYPOCALCEMIA)

as soon as patient is able too swallow -> higher doses of oral calcium (3 - 4g daily in 3 - 4 doses)

Question 11

What is the goal of long term management of hypocalcemia?

Answer 11

• maintain serum calcium within asymptomatic range
• calcium + vitamin D + magnesium + thiazides

When calcium control is difficult
- give thiazide diuretics (>150mg/hr)

Question 12

Albright hereditary osteodystrophy occurs due to?

Answer 12

Pseudohypothyroidism -> GNAS1 gene mutation

- short stature, round face, brachydactyly, obesity, & subcutaneous calcifications

Question 13

What’s the disease variation is case of mother or father inheriting?

Answer 13

If from mother -> all signs of AHO + multiple hormone resistance
If from father -> AHO without resistance

Question 14

How should PHP & iPPSD be treated?

Answer 14

• maintain total & ionized calcium levels within reference range to suppress PTH levels
• calcitriol, with oral calcium supplements
• severe symptomatic hypocalcemia -> IV calcium