Primary hyperparathyroidism can be treated medically when no specific indications for surgery exist. Short-term studies with bisphosphonates demonstrate lowering of serum calcium levels with decreases in bone resorption, but an increase in parathyroid hormone (PTH) levels. Parker and associates studied the long-term effects of alendronate on bone mineral density (BMD) and the safety of long-term therapy.
Thirty-two patients (27 women and five men) with primary hyperparathyroidism confirmed by elevated calcium and PTH levels were divided into two groups. Participants with very low baseline BMD scores were given open-label alendronate, and those with higher BMD scores were not treated. Patients were followed for 24 months, had an annual dual-energy x-ray absorptiometry (DEXA) scan, and had frequent biochemical analyses.
Patients receiving alendronate had bone gain at all sites measured over the first year of treatment, but significance was obtained only at the lumbar spine. Short-term fluctuations in serum calcium and PTH levels were noted in the treatment group, but these levels returned to normal baseline values after three months. Four patients receiving alendronate developed dyspepsia, one was taken out of the study early because of severe symptoms, and another withdrew after 18 months because of persistent symptoms. In the no-treatment group, only one patient developed dyspepsia.
The authors conclude that alendronate therapy improves BMD scores in the first year of therapy, primarily at the lumbosacral spine. The gains are less at the hips and radial sites. Bisphosphonates improve bone density most effectively in patients with the lowest BMD scores, making intergroup comparisons difficult. Alendronate may be helpful in patients with hyperparathyroidism and low BMD scores who are not candidates for parathyroidectomy, but further long-term studies are needed. Alendronate is well tolerated, with dyspepsia occurring most often in patients who had a history of dyspepsia and no evidence of renal toxicity.