Parathyroid

Question 1

Describe the feedback system of parathyroid hormone

Answer 1

Low ionised calcium = secretion of parathyroid hormone (PTH)

PTH increases in osteoclast activity = release of calcium and phosphate form bones & increase in calcium but decrease in phosphate reabsorption in kidney = high plasma calcium level but low plasma phosphate.

Question 2

Causes of Primary Hyperparathyroidism

Answer 2

~80% solitary adenoma
~20% hyperplasia of all glands
<0.5% parathyroid cancer

Question 3

Clinical Presentation of Hyperparathyroidism

Answer 3

1. High calcium = weak, tired, depressed, thirsty, dehydrated. Renal stones, abdo pain, pancreatitis and ulcers.
2. Bone resorption effects of PTH = pain, fractures, osteopenia/osteoporosis
3. High blood pressure

Question 4

Investigation of hyperparathyroidism

Answer 4

• Calcium and PTH is high / Calcium high and PTH inappropriately normal
• 24 hr urine shows increase calcium
• low phosphate
• Dexa scan - check for osteoporosis
• KUB X-ray/US - check for stones
• Biopsy if carcinoma suspected

Question 5

Management of hyperparathyroidism

Answer 5

If mild: just surveillance 6 monthly

• increase fluid intake to reduce risk of stones.
• avoid thiazides and high calcium and high vit d intake

Surgery:
- parathyroidectomy in most symptomatic patients

Question 6

Describe Secondary Hyperparathyroidism and its cause

Answer 6

Hyperparathyroidism triggered by chronic low calcium due to kidney, liver or bowel disease.
e.g. chronic renal failure

Question 7

Management of secondary hyperparathyroidism

Answer 7

• correct causes
• phosphate binders e.g. lantharium
• cinacalcet: increase sensitivity of parathyroid cells to calcium so that less PTH is secreted

Question 8

Describe tertiary hyperparathyroidism and when it occurs

Answer 8

autonomous secretion of PTH. therefore calcium high and PTH very high (inappropriately).

Occurs after prolonged secondary hyperparathyroidism causing glands to act autonomously having undergone hyper plastic/adenomatous changes.

Seen in chronic renal failure.

Question 9

Describe primary hypoparathyroidism

Answer 9

PTH secreation is decreased due to gland failure

Question 10

What are the causes of hypoparathyroidism

Answer 10

Autoimmune

Congenital

Question 11

Investigation of hypoparathyroidism (what would you find in the blood results)

Answer 11

low calcium, high or normal phosphate, normal alk phos.

Question 12

Describe the clinical features of hypoparathyroidism

Answer 12

Clinical features of hypocalcaemia:
Spasms
Periooral paraesthesia
Anxious, irritable, irrational
Seizures
Muscle tone - increase in smooth muscle: colic, wheeze, dysphagia
Orientation impairment and confusion
Dermatitis
Impetigo hepatiformis
Chvostek's sign - choreoathetosis, cataract, cardiomyopathy