Teriparatide

Osteoporosis-related fractures are a serious problem for older people. It is often a hip fracture that leads to decline in the health of the elderly. A third of all hip fractures occur in men, and almost 38% of those men will die in the following year. Osteoporosis in men is underdiagnosed. Generally defined as the thinning of bone tissue and decrease in density, osteoporosis is the most common type of bone disease.

The other treatments for osteoporosis are medications that prevent bone resorption. Bisphosphonates alendronate (Fosamax) and risedronate (Actonel) are oral medications. Other treatments include salmon calcitonin (Miacalsin) which is available as a nasal spray or injection. Raloxifene (Evista) is a selective estrogen receptor modulator. By preventing bone resorption, these medications are used to prevent bone loss.

Teriparatide is a synthetic form of the naturally occuring parathyroid hormone. Unlike other osteoporosis drugs, it actually causes bone density to increase. In the body, parathyroid hormone is released by the parathyroid glands in the neck (behine the thyroid glands) and is an important regulator in the bloodstream's levels of calcium and phosphorus. Laboratory tests can determine the level of this hormone in the blood.

The most important endpoint for treatment with any of these drugs is prevention of fractures, especially hip and vertebral fractures. A recent scientific study suggested teriparatide could be useful for treatment of osteoarthritis. The medicine may promote the formation of new cartilage tissue, which other arthritis treatments do not. It was a small study and more work will be needed before teriparatide starts to be used for arthritis regularly.

Bone metabolism is a complex process. Bone remodels throughout a person’s life, so that there is new bone being made along with bone resorption. Among the substances that affect bone metabolism are vitamin D, calcium, estrogen, testosterone, and parathyroid hormone which regulates the calcium and bone formation in the body. Other external factors influence bone metabolism and increase the risk of osteoporosis, including prolonged use of corticosteroids, alcoholism, smoking, and in men, hypogonadism.

Early trials of teriparatide leading to its FDA approval were completed separately for men and women. Evaluation of drugs for osteoporosis are complicated by the difficulty of knowing how severe the bone loss is, and also because treatment is needed not just to prevent thinning bone but to definitively protect against fracture.

One randomized trial of postmenopausal women who had already fractured vertebra compared teriparatide at either 20 or 40 micrograms per day with placebo. After about 19 months, 14% of the women taking placebo had new vertebral fractures, as compared with 5% of the women taking 20 micrograms of teriparatide and 4% of the women taking 40 micrograms. There were also a statistically significant lower number of non-vertebral fractures in the teriparatide treated group. 20 micrograms of teriparatide increased spine and hip bone mineral density. However, this study had to be terminated because 1.6% of the women taking 40 micrograms of teriparatide and 0.2% of those taking 20 micrograms developed significant increases in serum calcium, the amount of calcium in the blood, which can be dangerous.

Another trial compared 40 micrograms of teriparatide to alendronate. After about 14 months later, bone density increased more in the spine and femoral neck (part of the hip) in the patients treated with teriparatide. Bone density in the wrist decreased with teriparatide. Fewer patients treated with teriparatide suffered nonvertebral fractures.

A randomized trial using teriparatide to treat men with osteoporosis (half of whom had low testosterone levels) showed that teriparatide doses of both 20 micrograms and 40 micrograms increased bone density in the lumbar spine and the femoral neck. In this study bone density in the wrist decreased.