Randomized trial of pamidronate in patients with thyroid cancer: Bone density is not reduced by suppressive doses of thyroxine, but is increased by cyclic intravenous pamidronate

Patients taking suppressive doses of T-4 are thought to have accelerated bone loss and increased risk of osteoporosis. We therefore randomize 55 patients taking suppressive doses of T-4 to treatment with pamidronate (APD) 30 mg iv every 3 months for 2 yr (APD/T-4), or placebo (placebo/T-4). Patients had measurements of bone mineral density (BMD) of the spine, hip, radius, and total body every 6 months for 2 yr. There was no significant bone loss at any site in the placebo/T-4 group. Ninety five percent confidence intervals excluded a rate of bone loss >0.89%/yr for the spine and >0.31%/yr at the total hip. When men were excluded from the analysis, there still was no significant bone loss for the placebo/T-4 group, and confidence intervals did not change. The APD/T-4 group showed increases in spine (4.3%, P = 0.0001), total hip (1.4%, P < 0.05), and trochanteric (3.0%, P = 0.0001) BMDs. In conclusion, premenopausal women and men on suppressive therapy with T-4 do not lose bone rapidly, and are not at increased risk of developing osteoporosis. A regimen of 30 mg APD given every 3 months for 2 yr causes significant suppression of bone resorption and increases in BMD, and maybe an acceptable alternative treatment for osteoporosis in patients who cannot tolerate oral bisphosphonates.