Hyperparathyroidism

Question 1

What is hyperparathyroidism?

Answer 1

“Abnormally high PTH levels in blood due to overactivity of the parathyroid glands”
- PTH → increases serum calcium & decreases serum phosphate. Secretion is stimulated by decrease in serum calcium.

Question 2

Describe the epidemiology of hyperparathyroidism?

Answer 2

• F>M (3:1)
• most cases occur >50 yrs old

Question 3

What are the different types of hyperparathyroidsm?

Answer 3

1. Primary Hyperparathyroidism - increased secretion of PTH unrelated to the plasma calcium concentration or (inappropriately NORMAL given the raised calcium)
2. Secondary Hyperparathyroidism - increased secretion of PTH secondary to hypocalcaemia
3. Tertiary Hyperparathyroidism - autonomous PTH secretion (despite high calcium) following chronic secondary hyperparathyroidism – glands undergo hyperplastic or adenomatous changes.

Question 4

What are the causes of hyperparathyroidism?

Answer 4

1. Primary
   o Parathyroid adenoma 80%
   o Parathyroid hyperplasia 20%
   o Parathyroid carcinoma <0.5%
   o MEN syndrome
2. Secondary
   o Chronic renal failure
   o Vitamin D deficiency – causes reduced calcium absorption in gut hence hypocalcaemia
   - Pure vitamin D deficiency would lead to low calcium and phosphate
3. Tertiary:
   o Occurs after prolonged secondary hyperparathyroidism due to conditions like chronic kidney disease.

Question 5

Summarise the epidemiology of hyperparathyroidism

Answer 5

● Primary - incidence of 5/100,000
● Twice as common in FEMALES
● Peak incidence: 40-60 yrs

Question 6

What are the presenting symptoms and signs of hyperparathyroidism?

Answer 6

1. pHPT → polydipsia, polyuria, anorexia, nausea, constipation, bone pain (esp. back pain), renal stones, low mood.
   - Majority of patients are asymptomatic, abdominal groans & psychic moans (Symptoms of Hypercalcaemia)
2. sHPT + tHPT → symptoms related to underlying cause (ie. renal failure).
   - Bone pain and increased risk of fractures.

Question 7

What investigations are used to diagnose/ manage hyperparathyroidism?

Answer 7

1. U&Es
2. Serum calcium (high in primary and tertiary, low/normal in secondary)
3. Serum phosphate (low in primary and tertiary, high in secondary)
4. Albumin
5. ALP
6. Vitamin D
7. PTH - high
   Primary Hyperparathyroidism:
   o Hyperchloraemic acidosis
   o Normal anion gap
   o Due to PTH inhibition of renal reabsorption of bicarbonate
   o Urine - high PTH in the presence of high calcium can also be caused by familial hypocalciuric hypercalcaemia (FHH)
   *Calcium: creatinine clearance ratio can help differentiate between primary hyperparathyroidism and FHH
8. Renal ultrasound - can visualise renal calculi
9. DEXA scan to check bone density 

Question 8

How is hyperparathyroidism managed?

Answer 8

1. pHPT → total parathyroidectomy (definitive management). Calcimimetics (Cinacalcet) are drugs that inhibit PTH release.
   - IV Fluids for treat hypercalcaemia
2. sHPT → treat underlying cause (ie. CKD, Vitamin D deficiency)

Question 9

What are some complications that may arise from hyperparathyroidsim?

Answer 9

1. Primary
   o Increased bone resorption
   o Increased tubular calcium reabsorption
   o Increased 1-hydroxylation of vitamin D
   o All of these lead to hypercalcaemia
2. Secondary
   o Increased stimulation of osteoclasts and increased bone turnover
   o This leads to osteitis fibrosa cystica – seen on X-ray as subperiosteal erosions, cysts, brown tumours, pepper pot skull
3. Complications of surgery
   o Hypocalcaemia
   o HypoPTH
   o Recurrent laryngeal nerve palsy

Question 10

Summarise the prognosis for patients with hyperparathyroidism

Answer 10

● Primary - surgery is curative for benign disease in most cases
● Secondary or Tertiary - same prognosis as chronic renal failure