Hyperparathyroidism, Secondary

• • Induced abnormality of endogenous mechanisms that ensure calcium homeostasis

  • Increased parathyroid hormone (PTH) secretion in response to low plasma concentration of ionized calcium

  • Can see a hyperplasia of parathyroid chief cells

Epidemiology

• • Secondary hyperparathyroidism develops in 1-28% of patients who undergo dialysis

Symptoms and Signs

• • Similar symptoms to primary hyperparathyroidism

  • Complaints of significant bone pain

Laboratory Findings

• • Elevated intact PTH level

  • Low or normal serum calcium level

  • Elevated serum phosphorous level (when results from renal disease)

  • Normal or low serum phosphorous level (when results from malabsorption or rickets)

Imaging Findings

• • Similar (or more severe) skeletal changes as seen with primary hyperparathyroidism

• • In patients with secondary hyperparathyroidism, a higher serum calcium concentration is needed to suppress PTH secretion

  • Associated with renal disease as well as malabsorption syndromes

  • Almost universal complication of hemodialysis and peritoneal dialysis

  • When associated with renal disease, often due to phosphate retention, failure of kidneys to generate 1,25 dihydroxyvitamin D, resistance of bones to PTH action, and decreased serum calcium concentration

• • Measure serum intact PTH level

  • Measure serum calcium and phosphorous level

• • Goal is to decrease stimulation of the parathyroid gland by limiting serum hyperphosphatemia and supplementing both calcium and vitamin D

  • Will often resolve after correction of renal function (ie, with renal transplantation)

Surgery

• • Subtotal parathyroidectomy or total parathyroidectomy with parathyroid autograft

Indications

• • Hypercalcemia

  • Normocalcemia with severe renal osteodystrophy, bone pain, elevated alkaline phosphatase, bone fracture, torn tendon, pruritus, soft-tissue calcification, calciphylaxis, enlarged parathyroid gland

Medications

• • PO or IV calcitriol

  • Adjusting calcium and phosphorous concentration in dialysate solutions

  • Limiting phosphorous intake

  • Phosphate binders

  • Nonhypercalcemic vitamin D derivative and calcimimetics are being developed

Treatment Monitoring

• • Serum calcium and intact PTH levels

Complications

• • Profound hypocalcemia following subtotal parathyroidectomy for renal osteodystrophy, both because of "hungry bones" and because of decreased PTH secretion

  • Mortality is < 1% for parathyroidectomy in patients with secondary hyperparathyroidism despite significant comorbidities

Prognosis

• • 1-10% of patients who undergo successful kidney grafting have persistent secondary hyperparathyroidism and hypercalcemia

Prevention

• • Should start early in the course of chronic renal failure when intact PTH is normal or only slightly elevated

References