Hyperparathyroidism

Hyperparathyroidism is a condition characterised by increased levels of parathyroid hormone (PTH) in the blood. This can arise from a disorder within the parathyroid glands (primary hyperparathyroidism) or as a response to external stimuli such as vitamin D deficiency or chronic kidney disease (secondary hyperparathyroidism).

Signs and Symptoms

Hyperparathyroidism often presents with elevated blood calcium levels, which can lead to various symptoms. In primary hyperparathyroidism, about 75% of individuals are asymptomatic, with the condition often discovered incidentally during routine blood tests.

Symptomatic individuals may experience kidney stones, bone pain, weakness, depression, confusion, increased urination, and gastrointestinal distress. Long-standing hyperparathyroidism can result in osteoporosis due to the weakening of bones.

Secondary hyperparathyroidism, typically due to vitamin D deficiency or chronic kidney disease, manifests with bone disorders such as rickets in children or osteomalacia and renal osteodystrophy in adults.

Causes

Primary hyperparathyroidism is usually caused by a single benign tumour known as a parathyroid adenoma (80% of cases). Multiple adenomas or parathyroid cancer are less common causes.

Secondary hyperparathyroidism is often due to vitamin D deficiency, chronic kidney disease, or conditions leading to low blood calcium levels.

Diagnosis

Diagnosis of hyperparathyroidism is confirmed by elevated blood calcium and PTH levels. The specific type of hyperparathyroidism is determined by additional tests measuring serum phosphate and vitamin D levels.

Primary hyperparathyroidism shows high calcium and PTH levels with low phosphate levels. Secondary hyperparathyroidism typically presents with low calcium and vitamin D levels, high phosphate, and elevated PTH levels.

Tertiary hyperparathyroidism, seen in chronic kidney disease, has high calcium, phosphate, and PTH levels with low vitamin D levels.

Treatment

Primary Hyperparathyroidism

Treatment often involves surgical removal of the overactive parathyroid gland(s). Surgery is curative and indicated for symptomatic patients or those with complications such as kidney stones, osteoporosis, or high calcium levels.

In asymptomatic patients, monitoring may be sufficient.

Secondary Hyperparathyroidism

Management focuses on addressing the underlying cause, such as vitamin D supplementation or treatment of chronic kidney disease. Phosphate binders and dietary modifications may also be necessary to control phosphate levels.

Tertiary Hyperparathyroidism

Parathyroidectomy is indicated for severe cases, particularly in patients with persistent hypercalcaemia, bone pain, or fractures.

Medications

Cinacalcet, a calcimimetic, can be used to lower PTH levels in patients who are not candidates for surgery. It is particularly useful in managing secondary hyperparathyroidism in dialysis patients.

However, it carries risks such as hypocalcaemia and vomiting.

Epidemiology

Hyperparathyroidism affects approximately 2 per 1,000 people in the developed world. Primary hyperparathyroidism is more common in women and is typically diagnosed between ages 50 and 60.

Secondary hyperparathyroidism is prevalent among individuals with chronic kidney disease and vitamin D deficiency.

In summary, hyperparathyroidism is a condition that leads to elevated PTH and calcium levels, with various underlying causes and treatment options depending on the type and severity of the disease.

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Self-assessment MCQs (single best answer)

What is the most common cause of primary hyperparathyroidism?

Which symptom is most commonly associated with hyperparathyroidism?

What laboratory finding is typical in primary hyperparathyroidism?

Which of the following is NOT a common symptom of hyperparathyroidism?

Secondary hyperparathyroidism is often caused by which of the following conditions?

Which treatment is considered curative for primary hyperparathyroidism?

What is the mechanism by which parathyroid hormone increases blood calcium levels?

Which of the following is a diagnostic feature of secondary hyperparathyroidism?

What complication is most commonly associated with long-standing hyperparathyroidism?

Which imaging modality is commonly used to localise overactive parathyroid glands before surgery?