Hyperparathyroidism

Types and Causes

Primary Hyperparathyroidism (PHPT):

• Caused by parathyroid adenoma (85%), parathyroid hyperplasia (15%), or parathyroid cancer (5%).

• Leads to elevated parathyroid hormone (PTH) levels, usually with elevated calcium levels and low/normal phosphorus.

• Clinical presentation often asymptomatic, but hypercalcaemia may be detected incidentally.

• Common Signs and Symptoms: Bone pain, kidney stones, gastrointestinal symptoms (nausea, constipation), and neuropsychiatric manifestations.

Secondary Hyperparathyroidism (SHPT):

• Occurs as a response to hypocalcemia typically from chronic kidney disease (CKD) or vitamin D deficiency.

• Increased PTH secretion due to low calcium but typically with normal or low calcium levels.

Tertiary Hyperparathyroidism:

• Occurs as a progression of secondary hyperparathyroidism, usually in long-standing CKD.

• Autonomously functioning parathyroid glands after prolonged secondary hyperparathyroidism, leading to high PTH and calcium levels.

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Blood Test Interpretation

• Primary Hyperparathyroidism: Raised PTH, raised calcium, low phosphorus.

• Secondary Hyperparathyroidism: Raised PTH, normal/low calcium, high/normal phosphorus.

• Tertiary Hyperparathyroidism: Very high PTH, high calcium, raised phosphorus.

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Pathophysiology

PTH acts on kidneys, bones, and intestines to increase serum calcium levels:

• Kidneys: Increased calcium reabsorption and decreased phosphorus reabsorption.

• Bones: Increased bone resorption, releasing calcium and phosphorus.

• Intestines: Enhanced absorption of calcium via active vitamin D.

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Clinical Features

Skeletal:

• Bone disease (osteopenia, osteoporosis, osteitis fibrosa cystica).

• Increased risk of fractures.

• Salt and pepper skull appearance on imaging.

Renal:

• Nephrolithiasis (kidney stones).

• Nephrocalcinosis.

• Polyuria and polydipsia.

• Reduced renal concentrating ability.

Gastrointestinal:

• Anorexia, nausea, vomiting, constipation.

• Peptic ulcer disease and pancreatitis.

Neurological:

• Fatigue, depression, confusion.

• "Stones, bones, abdominal groans, and psychic moans" mnemonic for hypercalcaemia symptoms.

Cardiovascular:

• Hypertension, bradycardia.

• Shortened QT interval.

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Investigations

• Calcium and Phosphorus: Elevated serum calcium, low serum phosphorus (PHPT).

• PTH Level: Elevated in PHPT and SHPT.

• 24-hour urinary calcium excretion:

  • Helps differentiate PHPT from familial hypocalciuric hypercalcaemia (FHH).

• Vitamin D levels: Important in assessing SHPT.

• Bone Density Scan: To assess for osteoporosis.

• Imaging:

  • Sestamibi scan or ultrasound for parathyroid adenoma.

  • CT scan for detailed imaging, especially preoperatively.

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Management

Primary Hyperparathyroidism:

• Parathyroidectomy is the definitive treatment for symptomatic cases or in patients with complications (e.g., nephrolithiasis, osteoporosis).

• For patients who are not surgical candidates:

  • Maintain hydration (2.5L/day).

  • Avoid calcium and vitamin D supplements.

  • Use of bisphosphonates to prevent bone resorption.

  • Cinacalcet (calcimimetic) to reduce serum calcium levels.

Secondary Hyperparathyroidism:

• Treat underlying cause (e.g., vitamin D deficiency).

• Vitamin D analogues (e.g., calcitriol) and phosphate binders in CKD.

• Cinacalcet may also be used to control PTH levels.

Tertiary Hyperparathyroidism:

• Parathyroidectomy in severe cases.

• Phosphate binders and vitamin D analogues to manage calcium and phosphate levels.

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Notes:

Familial Hypocalciuric Hypercalcaemia (FHH):

• Genetic condition that can mimic PHPT with elevated serum calcium but with low urinary calcium excretion.

• Does not require surgery; usually benign and managed conservatively.

Monitoring:

• Regular follow-ups with serum calcium, phosphorus, and PTH levels.

• Bone density assessment, particularly in postmenopausal women and elderly patients