Parathyroid Hormone (1-84) and Risk for Spinal Fractures in Women with Osteoporosis

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The summary below is from the full report titled "Effect of Recombinant Human Parathyroid Hormone (1-84) on Vertebral Fracture and Bone Mineral Density in Postmenopausal Women with Osteoporosis. A Randomized Trial." It is in the 6 March 2007 issue of Annals of Internal Medicine (volume 146, pages 326-339). The authors are S.L. Greenspan, H.G. Bone, M.P. Ettinger, D.A. Hanley, R. Lindsay, J.R. Zanchetta, C.M. Blosch, A.L. Mathisen, S.A. Morris, and T.B. Marriott, for the Treatment of Osteoporosis with Parathyroid Hormone Study Group.

What is the problem and what is known about it so far?

People with osteoporosis have bones that become less dense and are more likely to break. The breaks most often occur at the hip, spine, and wrist. Risk factors for osteoporosis include older age, white or Asian ethnicity, and smoking. Drugs that slow bone breakdown or stimulate bone buildup are used for treatment. Such drugs include alendronate, ibandronate, and risedronate. Drugs that stimulate bone buildup are relatively new, and they include 2 manufactured forms of a natural hormone known as parathyroid hormone (PTH).

Why did the researchers do this particular study?

To assess the ability of 1 of the 2 available forms of PTH to slow bone breakdown and prevent spine fractures.

Who was studied?

2679 postmenopausal women with osteoporosis at the hip or lower back.

How was the study done?

The researchers randomly assigned the women to receive a form of PTH known as PTH (1-84) or placebo. Both were given as a once-daily shot. The researchers then compared the number of patients with new spine fractures and measures of bone growth, including bone mineral density and bone turnover markers, in the 2 groups over the next 18 months.

What did the researchers find?

Women who took PTH (1-84) had fewer fractures and higher bone mineral density levels than those who took placebo. Parathyroid hormone (1-84) caused more women to be nauseated and to have higher-than-normal levels of calcium in their urine and blood. The high calcium levels were not surprising given how the hormone works in the body.

What were the limitations of the study?

Researchers had to make assumptions about the number of fractures that occurred in the many women who left the trial early. The degree to which PTH (1-84) reduces fractures depends on the accuracy of those assumptions.

What are the implications of the study?

Parathyroid hormone (1-84) is a treatment option for postmenopausal women with osteoporosis who want to prevent spine fractures. It reduced the risk for spine fractures but also caused nausea and higher-than-normal urine and blood calcium levels.