The Role of Hormone Replacement Therapy (HRT) and Tibolone in the Prevention and Treatment of Postmenopausal Osteoporosis

Life expectancy has increased considerably in recent decades thanks to the improvement of measures for health protection and disease prevention as well as improvements in the quality of health systems. While in the middle of last century the average life expectancy of a woman was about 50 years, today there are over 350 million women older than 60. Furthermore, from the perspective of developed countries, postmenopause is a stage that spans more than one third of the life of a woman. That is why the research on the pathophysiology and treatment of menopause has become necessary and important. The decrease in sex steroid production by the ovary that occurs in perimenopause and menopause is associated with a rapid loss of bone mass due to increased resorption. In the past two decades, multiple observational studies have noted the beneficial effect of hormone replacement therapy (HRT) in postmenopausal women's health, based mainly on the relief of symptoms associated with estrogen deprivation such as vasomotor and genitourinary symptoms. These studies also indicated a preventive effect on aging-related diseases such as osteoporosis. Estrogens have been shown to be effective in increasing bone mineral density (BMD) and prevent fractures, but information on side effects from long use has reduced their use for the treatment of osteoporosis (Tamborini & Ruiz, 2004). Tibolone is a synthetic steroid used in the treatment of postmenopausal symptoms and decreased libido that has an estrogen agonist effect on bone. Although the intimate mechanisms of control of bone remodelling are not still completely known, we do have enough information to say that estrogens have a role in the homeostasis of the skeleton, which is why their decline is associated with reduced bone mass, impaired in the microarchitecture and increased risk of fracture. The following chapter discusses the role of estrogen therapy and tibolone in the prevention and treatment of postmenopausal osteoporosis.