Osteoporosis and parathyroid hormone.




New England Journal of Medicine

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Osteoporosis is condition in which the bones in our body become less dense and have a greater chance of breaking. This condition typically occurs in women over the age of 50, and is responsible for 300,000 hip fractures annually.1 Some issues can increase the chances of osteoporosis such as high caffeine intake, smoking, alcohol abuse, and lack of exercise. Researchers are not exactly sure why this decrease in bone strength happens. We do know that as we age, our body's ability to absorb calcium diminishes, and estrogen plays an important role in this absorption. As women age, the estrogen levels decline. Osteoblasts (bone cells) also decrease their ability to rebuild bone the older we get.

Many women who have osteoporosis begin hormone therapy to prevent and slow down bone loss. In fact, this therapy has shown to even replace bone loss that has already occurred.2 Additional factors that help to decline bone loss include supplementation of calcium and vitamin D. Weight bearing exercise may also be recommended. Many researchers are still trying to find new and alternative ways to prevent and treat osteoporosis.

A recent study published in the May 2001 issue of New England Journal of Medicine, examined the effects of parathyroid hormone on bone loss. The parathyroid hormone is a substance secreted by our parathyroid gland and helps to regulate the absorption of calcium and phosphorus. The study involved 1,637 postmenopausal women who have had past vertebral fractures due to osteoporosis. The women received once daily injections of placebo, or 20 or 40 ìg of the hormone. They measured vertebral bone loss by a dual energy x-ray machine. This 21-month study has positive results. 14 % of the women who received placebo experienced additional vertebral fractures. Only 5% of the women who received 20 ìg of parathyroid hormone had fractures, and there was only a 4% occurrence reported in the group receiving 40 ìg. Both doses of the parathyroid hormone increased the total body bone mineral density by 2 and 4% respectively. Minor side effects occurred such as nausea and headache. The authors concluded that treatment of postmenopausal osteoporosis with this hormone resulted in decreased fractures and increased bone mineral density. The higher dose was associated with heightened side effects.3


1. National Osteoporosis Foundation, 1999.
2. Masiukiewicz US, et al. Estrogen modulates parathyroid hormone-induced interleukin-6 production in vivo and in vitro. Endocrinology. Jul2000;141(7):2526-31.
3. Neer RM, et al. Effect of Parathyroid Hormone (1-34) on Fractures and Bone Mineral Density in Postmenopausal Women with Osteoporosis. NEJM. May 10 2001;334:1434-1441.