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Parathyroid Hormone More Effective Alone than When Combined with Alendronate for Osteoporosis: Presented at ASBMR

By Mary Beth Nierengarten

MINNEAPOLIS, MN -- September 24, 2003 -- Alendronate does not seem to provide additional benefits to parathyroid hormone (PTH) in postmenopausal women being treated for osteoporosis, suggests a new study presented here September 19^th at the 25^th Annual Meeting of the American Society for Bone and Mineral Research.

Dennis Black, PhD, lead investigator, University of California, San Francisco, said the study was conducted to determine whether alendronate, which reduces bone resorption, would have an additive or synergistic effect when combined with PTH, which stimulates bone formation, in the treatment of osteoporosis.

In addition to a lack of additive or synergistic effect, said Dr. Black, PTH alone was actually dramatically better in increasing bone mineral density (BMD) of the trabecular spine than the combined regimen.

The multicentre, randomized study enrolled 238 postmenopausal women with low hip or spine bone mass density (T-score of less than –2.5 or less than –2.0 with a risk factor for osteoporosis) that received no prior treatment for osteoporosis. Dr. Black and colleagues evaluated the bone density of the hip and spine in 119 women who were randomised to a daily regimen of human recombinant PTH 100 mcg (1-84) alone, 59 to alendronate 10 mg alone, and 60 to combined therapy.

At a mean of 1 year, measures of changes to bone mass showed a significant increase in spine trabecular bone mass with PTH alone compared with combined therapy (P=0.001) or alendronate alone (P=0.001). In the spine, increases in BMD were comparable between PTH and combined therapy, with a non-significant increase between these two regimens compared to alendronate alone (P=0.09).

Although alendronate alone or combined with PTH did show greater BMD increases in the femoral neck than PTH alone, increases in the corticol volume at the hip were significantly greater with PTH alone than alendronate alone (P<0.001) or combination therapy (P=0.002).

Overall, the large increases in bone formation and resorption in patients treated with PTH alone, and the slight decreases in patients treated with the combined regimen, suggest that PTH should be used alone, Dr. Black said.

The researchers emphasise the need for longer and larger studies to further examine if and how alendronate and other bisphosphonates should be combined with PTH.

"A particularly important question that was not addressed by this study, and is important for many women, is the effects of adding PTH to treatment of patients already taking alendronate," said Dr. Black.


[Study title: The Effects of PTH, Alendronate alone or in combination on bone mass and turnover: 12 month results of the PATH trial. Abstract 1007]

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