The factors responsible for the development of secondary HPT, including hypocalcemia, hyperphosphatemia, and vitamin D deficiency, should be corrected.11 Early treatment is of value to prevent bone disease. Overall, only about 5% of patients with chronic renal failure on dialysis require parathyroidectomy. A diet low in phosphorus and high in phosphorus binders should be prescribed to keep serum phosphate levels normal. Phosphate binders containing aluminum hydroxide should be avoided or used intermittently to avoid aluminum bone disease. This diagnosis should be kept in mind in the differential diagnosis of patients with bone pain and renal osteodystrophy. The diagnosis can be made with bone biopsy, and most patients with aluminum bone disease do not have markedly increased PTH levels or alkaline phosphatase levels.12 Hypophos-phatemia, although uncommon, should also be avoided in patients with chronic renal failure as it may cause hypophosphatemic osteomalacia. A normal or low blood phosphate level, however, lessens the risk of soft tissue calcification.
Calcium supplementation is required since intestinal absorption of calcium is diminished in renal failure patients with reduced 1,25-dihydroxyvitamin D levels. Diets low in phosphate are usually also low in calcium. Calcitriol supplementation is mandatory and should be started even before the patient is dialysis dependent. During treatment with calcitriol, care should be taken to avoid hypercalcemia because it worsens renal function and causes metastatic calcifications, especially in individuals with high blood phosphate levels. The rare patient without an elevated PTH level does not require vitamin D supplementation (Figure 6-6).
PTH levels and parathyroid gland size should be evaluated when the selection of therapy is being considered. Patients with markedly increased PTH levels and parathyroid glands greater than 1 cm by ultrasonographic examination (Figure 6-7) or 0.5 g are almost never adequately controlled on medical therapy. Cessation of treatment always results in disease relapse. Parathyroid glands larger than 1 cm are also more resistant to calcitriol therapy.8 In such cases, medical therapy with pulse calcitriol loses its effectiveness and may also be dangerous because of increased hypercalcemia.
PTH should also not be overly suppressed in order to avoid adynamic bone disease. The metabolic acidosis in dialysis patients should be corrected. Charcoal hemoperfusion has been reported
to be effective for treatment of pruritus, but patients with severe pruritus and bone pain with secondary HPT benefit from parathyroidectomy. Bisphospho-nates, synthetic analogues of pyrophosphate, have recently been used to reduce bone resorption.
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