Hypoparathyroidism (E&M)

Question 1

Define hypoparathyroidism.

Answer 1

Disorder caused by relative or absolute deficiency of PTH synthesis and secretion, leading to low serum calcium and elevated serum phosphate

Question 2

What are the main causes of hypoparathyroidism? (4)

Answer 2

• postoperative - thyroidectomy, parathyroidectomy, laryngeal surgery, transient postoperative hypocalcaemia
• autoimmune
• nonautoimmune - Wilson disease, haemochromatosis
• congenital - DiGeorge syndrome

Question 3

What is pseudohypoparathyroidism?

Answer 3

Rare genetic condition resulting in failure of target organs to respond to normal levels of parathyroid hormone

Question 4

What are some clinical features of pseudohypoparathyroidism? (4)

Answer 4

• short stature
• short fingers
• symptoms of hypocalcaemia
• vitamin D deficiency

Question 5

What condition can develop into hypoparathyroidism?

Answer 5

Riedel thyroiditis

Question 6

What are the clinical features of hypoparathyroidism generally in line with?

Answer 6

Hypocalcaemia (increased neuromuscular excitability) - CATS go numb

(Convulsions, Arrhythmias, Tetany/Spasms, Paraesthesia)

Question 7

What are the clinical features of hypoparathyroidism? (4+4)

Answer 7

• convulsions
• arrhythmias (prolonged QT interval)
• tetany - muscle twitches, spasms, cramps
• paraesthesia, numbness, tingling
• malnutrition, malabsorption, diarrhoea
• chronic alcoholism
• poor memory + slowed thinking
• dry nails, brittle hair, cataracts

Question 8

What might we see on examination of hypoparathyroidism?

Answer 8

• Chvostek’s sign - contraction of facial muscles when facial nerve is tapped in front of ear
• Trousseau’s sign - painful clasping response of fingers and hands (carpopedal spasm) when BP cuff is inflated above systolic BP

Question 9

What other electrolyte abnormality has the same features as hypoparathyroidism?

Answer 9

Hypomagnesaemia

Question 10

What are some risk factors for hypoparathyroidism? (4)

Answer 10

• thyroid/parathyroid surgery
• hypomagnesaemia
• moderate and chronic maternal hypercalcaemia (neonatal hypocalcaemia)
• autosomal dominant conditions

Question 11

What are the first-line investigations for hypoparathyroidism? (4)

Answer 11

• serum calcium
• plasma intact PTH
• serum albumin
• ECG

Question 12

What important blood findings are there in hypoparathyroidism? (6)

Answer 12

• low PTH
• low serum calcium (and normal ALP)
• high serum phosphate
• normal serum albumin (low albumin = falsely low serum calcium)
• normal/low serum magnesium
• normal/low 25-OH vitamin D

Question 13

What would ECG show in hypoparathyroidism?

Answer 13

Isolated prolonged QT interval (predisposes to Torsades de Pointes)

Indicates severe life-threatening hypocalcaemia, treat with urgent IV calcium gluconate

Question 14

What are some differential diagnoses for hypoparathyroidism? (5)

Answer 14

• hypovitaminosis D - PTH high, vitamin D low
• hypomagnesaemia - low serum Mg
• hypoalbuminemia
• pseudohypoparathyroidism - elevated plasma intact PTH, target organs cannot respond
• CKD/renal failure - elevated serum creatinine and PTH

Question 15

How do we manage hypoparathyroidism? (2)

Answer 15

IV/oral calcium AND low dose calcitriol

Consider: human recombinant PTH + adjustment of calcium and/or calcitriol doses (in chronic disease)

Question 16

How do we manage severe hypocalcaemia (<1.88mmol/L) in hypoparathyroidism?

Answer 16

IV calcium

Hypomagnesaemia: plus parenteral magnesium

With respiratory alkalosis: plus Rx for alkalosis

ECG isolated prolonged QT –> urgent IV calcium gluconate

Question 17

How do we manage asymptomatic temporary postoperative hypocalcaemia (hypoparathyroidism)?

Answer 17

Oral calcium and low-dose calcitriol

Question 18

How do we manage chronic hypoparathyroidism?

Answer 18

Oral calcium + calcitriol +/- human recombinant PTH

With hypercalciuria: thiazide diuretic and low-salt diet

Question 19

What are some complications of hypoparathyroidism? (5)

Answer 19

• ectopic calcifications
• cataract
• hypercalcaemia (from Rx)
• renal insufficiency
• renal stones (from Rx)