Secondary hyperparathyroidism (SHPT) refers to persistent stimulation of the parathyroid glands caused by conditions such as hypocalcemia, leading to glandular hyperplasia and excessive secretion of parathyroid hormone (PTH). It is a common and severe complication in patients with chronic renal failure.
Etiology and Pathology
In the context of renal dysfunction or failure, calcium-phosphorus metabolism becomes disrupted due to multiple factors. First, impaired calcium reabsorption by renal tubules and reduced phosphate excretion contribute to imbalances. Second, 1,25-hydroxyvitamin D3 cannot be converted into its active form, 1,25-dihydroxyvitamin D3, reducing calcium absorption in the gastrointestinal tract. Prolonged hypocalcemia stimulates parathyroid hyperplasia and excessive PTH secretion as a compensatory response.
From a pathological perspective, secondary hyperparathyroidism primarily manifests as hyperplasia of the parathyroid glands. The degree of hyperplasia varies among the glands, often showing significant disparities.
Clinical Manifestations
Chronic elevation of PTH levels in secondary hyperparathyroidism can lead to symptoms involving multiple systems. Common manifestations include bone pain and fractures, vascular and tissue calcification, pruritus, muscle weakness, as well as neurological and psychiatric symptoms.
Diagnosis
Diagnosis is made based on the patient’s medical history and laboratory results, including measurements of serum calcium and PTH levels, which guide treatment initiation and serve as indicators of therapeutic efficacy.
For localization purposes, diagnostic imaging techniques such as cervical ultrasound, CT, and 99mTc-MIBI are utilized. However, glandular enlargement in secondary hyperparathyroidism is often less pronounced than in primary hyperparathyroidism, and the positivity rate of radionuclide imaging is lower. Thus, cervical ultrasound and CT are the preferred localization methods.
Treatment
Most patients can manage phosphorus, calcium, and PTH levels through dietary modifications, medications, and adequate dialysis. However, surgical intervention is recommended in cases where symptoms such as bone pain, osteoporosis, and severe pruritus significantly impair quality of life, PTH levels persistently exceed 800 ng/L, or when there is resistance to medications such as calcimimetic agents, vitamin D, and its analogs, as well as medically refractory hypercalcemia or hyperphosphatemia.
The selection of a surgical approach considers factors such as minimizing postoperative complications, reducing the likelihood of persistent secondary hyperparathyroidism, preserving sufficient parathyroid function, and accounting for potential renal transplantation in the future. Specific surgical approaches are determined by the individual patient’s condition and the surgeon's experience.
Currently, common surgical techniques include subtotal parathyroidectomy, total parathyroidectomy with autotransplantation, and total parathyroidectomy without autotransplantation.