Hypoparathyroidism

Question 1

What is the definition of hypoparathyroidism? [3]

Answer 1

underactive parathyroid glands / producing too little PTH / leading to decreased levels of Ca2+ in the blood plasma and hypocalcaemia

Question 2

What is the definition of hypocalcaemia? [3]

Answer 2

low Ca2+ in the blood serum / below 2.1mmol/L

apparent hypocalcaemia may be an artefact of hypoalbuminaemia

Question 3

What are the causes of hypoparathyroidism? [7]

Answer 3

1. chronic kidney disease - most common cause of hypocalcaemia
2. severe vitamin D deficiency
3. primary hypoparathyroidimsm
4. secondary hypoparathyroidism - most common cause of hypoparathyroidism
5. pseudohypoparathyroidism
6. pseudopseudoparahypoparathyroidism
7. other causes - drugs, acute pancreatitis, osteomalacia

Question 4

What is the pathophysiology of chronic kidney disease [3]

Answer 4

decreased production of calcitriol (active vitamin D) / and decreased renal phosphate retention / so low Ca2+ and high PO4(3)-

Question 5

What is the pathophysiology of severe vitamin D deficiency? [3]

Answer 5

decreased Ca2+ absorption from the gut / so mild or severe hypocalcaemia / results from reduced UV exposure, malabsorption, anit-epileptic drugs

Question 6

What is the pathophysiology of primary hypoparathyroidism? [4]

Answer 6

decreased PTH secretion due to parathyroid gland / so low Ca2+ and high PO4(3)- / caused by DiGeorge syndrome (congential condition) / or autoimmune idiopathic hypoparathyroidism

Question 7

What is the pathophysiology of secondary hypoparathyroidism? [3]

Answer 7

1. parathyroid/thyroid surgery
2. radiation
3. hypomagnesaemia - Mg2+ required for PTH secretion

Question 8

What is the pathophysiology of pseudohypoparathyroidism? [3]

Answer 8

failure of target cell response to PTH (PTH resistance) / low Ca2+ but high PTH / associated with short stature, short 4th & 5th metacarpals, intellectual impairment

Question 9

What is the pathophysiology of pseudopseudohypoparathyroidism? [3]

Answer 9

same morphological features of pseudohypoparathyroidism / but normal biochemistry (no defects in Ca2+ metabolism) / cause is genetic, inherited from father

Question 10

What drugs can cause hypoparathyroidism and how? [2]

Answer 10

1. calcitonin - decreases plasma Ca2+ and PO4(3)-

2. bisphosphonates - decreases osteoclast activity resulting in low Ca2+

Question 11

What are the signs of hypercalcaemia? [9]

Answer 11

1. spasms (carpopedal spams = Trousseau’s sign)
2. paraesthesia
3. anxious, irritable, irrational
4. seizures
5. muscle tone increases in smooth muscle - wheeze
6. orientation impaired and confusion
7. dermatitis/diarrhoea
8. impetigo herpetiformis
9. Chvostek’s sign, cataract, cardiomyopathy

Question 12

What is Chvostek’s sign? [2]

Answer 12

tapping over the facial nerve over the parotid / causes twitching of ipsilateral facial muscle

Question 13

What is Trousseau’s sign? [2]

Answer 13

carpopedal spasm (wrist and fingers flex and draw together) / induced by inflating blood pressure cuff above systolic BP

Question 14

How is hypoparathyroidism diagnosed? [4]

Answer 14

1. clinical history and pictures, confirmed by low serum Ca2+
2. low serum PTH levels
3. parathyroid antibodies in autoimmune idiopathic hypoparathyroidism
4. x-rays of metacarpals - short 4th & 5th metacarpals in pseudohypoparathyroidism

Question 15

What is the treatment for hypocalcaemia? [3]

Answer 15

1. severe symptoms - IV calcium gluconate
2. vitamin D deficiency - oral cholecalciferol or oral adcal
3. hypoparathyroidism - calcium supplements and calcitriol