Primary Hyperparathyroidism: Diagnostic Criteria and Laboratory Findings

Introduction

Primary hyperparathyroidism (PHPT) is an endocrine disorder characterized by excessive secretion of parathyroid hormone (PTH), leading to hypercalcemia. It is the most common cause of hypercalcemia and can have significant systemic effects.

Etiology

PHPT is primarily caused by:

Single parathyroid adenoma (most common, accounting for ~85% of cases)
Parathyroid hyperplasia (15%)
Parathyroid carcinoma (rare, <1%)

Clinical Features

Patients with PHPT may be asymptomatic or present with clinical manifestations including:

Hypercalcemia-related symptoms: fatigue, polyuria, nephrolithiasis, osteoporosis
Neuromuscular symptoms: weakness, depression
Gastrointestinal symptoms: nausea, constipation, peptic ulcer disease

Diagnostic Criteria

Diagnosis of PHPT is based on laboratory findings:

Elevated serum calcium (>10.5 mg/dL)
Elevated parathyroid hormone (PTH) (above normal reference range)
Low serum phosphate (due to increased renal excretion)
Increased urinary calcium excretion

Additional Laboratory Tests

Bone mineral density (DEXA scan) to evaluate osteoporosis
Serum 25-hydroxyvitamin D levels
Imaging studies: ultrasound, sestamibi scan

Treatment Options

Management strategies depend on symptoms and calcium levels:

Surgical removal (parathyroidectomy) for symptomatic patients or those with significant hypercalcemia
Medical therapy (calcimimetics like cinacalcet) for patients unsuitable for surgery
Monitoring for asymptomatic patients with mild hypercalcemia

Conclusion

Primary hyperparathyroidism is a significant endocrine disorder with systemic effects. Early diagnosis through laboratory testing is crucial for optimal management.