Parathyroid glands and disorders of calcium metabolism

Hyperparathyroidism

Disease type_Hormone profile_Clinical features_Cause| Primary hyperparathyroidism_

• PTH (Elevated)
• Ca2+ (Elevated)
• Phosphate (Low)
• Urine calcium : creatinine clearance ratio > 0.01_
• May be asymptomatic if mild
• Recurrent abdominal pain (pancreatitis, renal colic)
• Changes to emotional or cognitive state_

Most cases due to solitary adenoma (80%), multifocal disease occurs in 10-15% and parathyroid carcinoma in 1% or less| Secondary hyperparathyroidism_

• PTH (Elevated)
• Ca2+ (Low or normal)
• Phosphate (Elevated)
• Vitamin D levels (Low)_
• May have few symptoms
• Eventually may develop bone disease, osteitis fibrosa cystica and soft tissue calcifications_

Parathyroid gland hyperplasia occurs as a result of low calcium, almost always in a setting of chronic renal failure| Tertiary hyperparathyroidism_

• Ca2+ (Normal or high)
• PTH (Elevated)
• Phosphate levels (Decreased or Normal)
• Vitamin D (Normal or decreased)
• Alkaline phosphatase (Elevated)_
• Metastatic calcification
• Bone pain and / or fracture
• Nephrolithiasis
• Pancreatitis_

Occurs as a result of ongoing hyperplasia of the parathyroid glands after correction of underlying renal disorder, hyperplasia of all 4 glands is usually the cause| Differential diagnoses It is important to consider the rare but relatively benign condition of benign familial hypocalciuric hypercalcaemia, caused by an autosomal dominant genetic disorder. Diagnosis is usually made by genetic testing and concordant biochemistry (urine calcium : creatinine clearance ratio 1mg/dL above normal

• Hypercalciuria > 400mg/day
• Creatinine clearance < 30% compared with normal
• Episode of life threatening hypercalcaemia
• Nephrolithiasis
• Age < 50 years
• Neuromuscular symptoms
• Reduction in bone mineral density of the femoral neck, lumbar spine, or distal radius of more than 2.5 standard deviations below peak bone mass (T score lower than -2.5)

Secondary hyperparathyroidism Usually managed with medical therapy. Indications for surgery in secondary (renal) hyperparathyroidism:

• Bone pain
• Persistent pruritus
• Soft tissue calcifications

Tertiary hyperparathyroidism Allow 12 months to elapse following transplant as many cases will resolve The presence of an autonomously functioning parathyroid gland may require surgery. If the culprit gland can be identified then it should be excised. Otherwise total parathyroidectomy and re-implantation of part of the gland may be required. References 1. Pitt S et al. Secondary and Tertiary Hyperparathyroidism, State of the Art Surgical Management. Surg Clin North Am 2009 Oct;89(5):1227-39.

2. MacKenzie-Feder J et al. Primary Hyperparathyroidism: An Overview. Int J Endocrinol 2011; 2011: 251410.