Hyperparathyroidism

Question 1

What is hyperparathyroidism?

Answer 1

Primary: Increased secretion of parathyroid hormone (PTH) unrelated to the plasma calcium concentration Secondary: Increased secretion of PTH secondary to hypocalcaemia Tertiary: Autonomous PTH secretion following chronic secondary hyperparathyroidism

Question 2

What is the aetiology of hyperparathyroidism?

Answer 2

Primary: Parathyroid gland adenomas or hyperplasia. Rarely, parathyroid carcinoma. May be associated with multiple endocrine neoplasia (MEN) Secondary: Chronic renal failure, vitamin D deficiency

Question 3

What is the epidemiology of hyperparathyroidism?

Answer 3

Primary: Annual incidence if 5 in 100,000. Twice as common in females. Peak incidence 40-60 years

Question 4

What are the presenting symptoms of hyperparathyroidism and its signs on examination?

Answer 4

• Primary: Many patients have mild hypercalcaemia and are asymptomatic
• Hypercalcaemia may present with: polyuria, polydipsia, renal calculi, bone pain, abdominal pain, nausea, constipation, psychological depression and lethargy
• Secondary: May present with symptoms and signs of hypocalcaemia and/or the underlying cause (chronic renal failure, vit D deficiency)

Question 5

What are the investigations for hyperparathyroidism?

Answer 5

• U&E’s, serum calcium (raised in primary and tertiary, decreased or normal in secondary), Phosphate (low in 1&2, raised in 3), raised alkaline phosphatase, vit D (low in 2) - Primary: hyperchloraemic acidosis (normal anion gap) caused by PTH inhibition of renal tubular reabsorption of bicarbonate - Urine: Differential diagnosis of primary hyperparathyroidism includes familial hypocalciuric hypercalcaemia - Renal ultrasound at baseline to look for renal calculi - Radiographs - Preoperative localisation

Question 6

How is primary hyperparathyroidism managed?

Answer 6

• Acute hypercalcaemia: IV fluids. Conservative management: In patients who do not meet surgical criteria, avoid factors that can exacerabate hypercalcaemia including thiazide diuretics. Maintain adequate hydration (at least 6-8 glasses water per day). Moderate calcium & vit D intake - Surgical: Subtotal parathyroidectomy, total parathyroidectomy (in MEN1). Indications: symptomatic patients or asymptomatic patients with Age= over 50 Bone mineral density= T score less than 2.5 Creatinine clearance= reduced by 30% Difficult to do follow up periodically Elevated serum calcium

Question 7

How is secondary hyperparathyroidism managed?

Answer 7

Treat underlying renal failure Calcium and vitamin D supplements

Question 8

What are the possible complications of hyperparathyroidism?

Answer 8

• Primary: Raised PTH results in more bone resorption, raised renal tubular calcium reabsorption, 1a-hydroxylation of vit D and intestinal calcium absorption, leading to hypercalcaemia - Secondary: Increased stimulation of osteoclasts and bone turnover leading to osteitis fibrosa cystica - Complications of surgery: Hypocalcaemia, recurrent laryngeal nerve palsy

Question 9

What is the prognosis for hyperparathyroidism?

Answer 9

• Primary: surgery is curative for benign disease in most cases - Secondary or tertiary: As for chronic renal failure