Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis. (Abstracts of Current Literature).

Neer RM, Arnaud CD, Zanchetta JR, et al (Massachusetts General Hospital and Harvard Medical School, Boston, Mass; University of California, San Francisco, San Francisco, Calif; Fundacion de Investigaciones Metabolicas, Buenos Aires, Argentina), N Engl J Med. 2001;344:1434-1441.

The mode of administration influences the effect of parathyroid hormone, which is known to stimulate both bone formation and bone resorption and to increase and decrease bone mass. This study evaluated the effect of daily parathyroid hormone injections on women who were postmenopausal and had prior vertebral fractures. The outcome measures included both new vertebral and nonvertebral fractures and changes in bone mineral density (BMD).

All subjects (N=1,637) received daily calcium and vitamin D supplements. Serum calcium and creatinine excretion was measured at baseline and every 6 months during treatment. Changes in calcium supplementation or dosage were adjusted to maintain normal levels of serum and excretion. Baseline and end-of-study data were obtained from anteroposterior and lateral radiography of the thoracic and lumbar spine; serial data were obtained from dual-energy x-ray absorptiometry (DEXA) scans of the lumbar spine, proximal femur, radius, and total body; and height was measured with a stadiometer at baseline and every 12 months for the duration of the study. The study ran for approximately 21 months.

For the first 2 weeks, all subjects self-administered daily injections of placebo and then were randomized into 3 treatment groups. One group (n=544) continued to receive placebo injections, whereas the other groups received either 20 [micro]g (n=541) or 40 [micro]g (n=552) of parathyroid hormone (1-34) by daily self-administered injection.

The authors used Pearson's chi-square and ANOVA to look for differences among the groups. There were no statistical differences among the groups in any of the baseline characteristics such as age, body mass index (BMI), calcium intake, or lumbar spine BMD. The mean T-score of spinal BMD of the subjects was -2.6 at baseline. Adherence was assessed at each visit by quantifying the amount of medication returned by the subjects, and adherence ranged from 79% to 83%. Eighty-one percent of the subjects had available and adequate radiographs for follow-up.

The authors reported that parathyroid hormone (1-34) reduced the risk of 1 or more new vertebral fractures by 65% in the 20 [micro]g group and by 69% in the 40 [micro]g group. The risk of having 2 or more fractures was reduced by 77% and 86% respectively, and the risk of 1 or more severe vertebral fractures was reduced by 90% and 78%. Compared with the placebo treatment, 20 [mciro]g and 40 [micro]g of parathyroid hormone decreased the likelihood of new nonvertebral fractures by 35% and 40%, respectively. Parathyroid hormone also increased bone mineral density in the spine, hip, and total body. The 40 [micro]g dose increased bone mineral density more than the 20 [micro]g dose, but the 2 dosages had similar effects on reducing the risk of vertebral and nonvertebral fractures.

The authors concluded that the use of daily parathyroid hormone resulted in a dose-dependent increase in BMD in the spine and hip of women who are postmenopausal and osteoporotic and reduced the number and severity of new vertebral and nonvertebral fractures in a multinational cohort. The authors suggested that parathyroid hormone is an effective therapy for preventing fractures in women who are postmenopausal and have osteoporosis.

Nancey A Bookstein, PT, EdD
University of Colorado Health
Sciences Center
Denver, Colo