Hyperparathyroidism is characterized by elevated parathyroid hormone (PTH) levels, often affecting calcium and phosphate balance.
1. Primary Hyperparathyroidism
Cause:
- Autonomous overproduction of PTH by the parathyroid gland(s)
- Most common causes:
- Parathyroid adenoma (85%)
- Parathyroid hyperplasia (10–15%)
- Parathyroid carcinoma (<1%)
Labs:
| Marker | Level |
|---|
| PTH | ↑ |
| Calcium | ↑ |
| Phosphate | ↓ |
| 1,25(OH)₂ Vit D | ↑ or normal |
Clinical Features:
- Often asymptomatic (found on routine bloods)
- “Bones, stones, groans, and psychic overtones”:
- Bone pain/osteitis fibrosa cystica
- Renal stones
- Abdominal pain
- Neuropsychiatric symptoms
2. Secondary Hyperparathyroidism
Cause:
- Chronic hypocalcemia → compensatory increase in PTH
- Common causes:
- Chronic kidney disease (CKD)
- Vitamin D deficiency
- Malabsorption (e.g. celiac disease, bariatric surgery)
Labs:
| Marker | Level |
|---|
| PTH | ↑ |
| Calcium | ↓ or normal |
| Phosphate | ↑ (in CKD) |
| 1,25(OH)₂ Vit D | ↓ |
Clinical Features:
- Features of underlying disease (e.g. CKD)
- Bone pain, fractures (renal osteodystrophy)
- Calciphylaxis (in severe CKD cases)
3. Tertiary Hyperparathyroidism
Cause:
- Long-standing secondary hyperparathyroidism → autonomous PTH secretion
- Typically in end-stage renal disease after prolonged stimulation
Labs:
| Marker | Level |
|---|
| PTH | ↑↑ |
| Calcium | ↑ |
| Phosphate | ↑ |
Clinical Features:
- Often occurs after kidney transplantation
- Features of hypercalcemia + PTH remains elevated despite resolution of initial hypocalcemic stimulus
Summary Table:
| Type | PTH | Ca²⁺ | PO₄³⁻ | Cause |
|---|
| Primary | ↑ | ↑ | ↓ | Parathyroid adenoma/hyperplasia |
| Secondary | ↑ | ↓/N | ↑/↓ | CKD, Vit D deficiency |
| Tertiary | ↑↑ | ↑ | ↑ | Long-standing secondary (e.g., ESRD) |
