Daily and Cyclic Parathyroid Hormone in Women Receiving Alendronate

Abstract

Parathyroid hormone (PTH), unlike antiresorptive agents, which lessen bone remodeling, initially stimulates bone formation and later promotes remodeling. Recent findings pose a question of efficacy when administering PTH with alendronate whether or not women have been previously treated for osteoporosis. This study was designed to show whether PTH treatment can improve bone mineral density (BMD) and biochemical markers of bone turnover in women who had received, and were still receiving, alendronate. A regimen consisting of 3-month cycles of PTH treatment alternating with 3-month periods of no PTH was compared with daily treatment. A total of 126 women with osteoporosis who had taken alendronate for at least 12 months were randomized to continued alendronate plus PTH (1–34), self-injected subcutaneously each day; continued alendronate plus cyclical PTH treatment; or alendronate alone for 15 months. The dose of alendronate was 70 mg weekly and that of PTH was 25 μg daily whether given cyclically or continuously. Calcium and vitamin D were given when needed. Markers of bone formation increased with daily PTH but did not change significantly in alendronate-treated women. After 15 months, BMD at the lumbar spine had increased 6.1% in women given daily PTH and 5.4% in those given cyclical PTH. It did not change significantly in alendronate-treated patients. All but 15% of women given PTH had an increase in spinal BMD. Changes in biochemical markers and spinal BMD did not correlate with the duration of previous alendronate treatment. BMD at the hip increased slightly in all groups. In no group was there a significant change in total-body BMD. The rate of new or worsening vertebral deformities was 3% in women given daily PTH, 6% in those receiving cyclical PTH, and 1% in those on alendronate. None of the women required dose reduction because of side effects. These findings suggest that cyclical PTH treatment for 3-month periods with 3-month periods off PTH, like daily treatment, increases BMD in the spine in women who continue to have osteoporosis after receiving alendronate. Cyclical PTH has results similar to those achieved with daily treatment but at a lesser cost.