Effects of oral contraceptives on bone mineral density.

Osteoporosis is a major health problem that leads to a high incidence of spine, radial, and hip fractures. It is now well recognized that a chronically hypoestrogenic state increases bone turnover that, in turn, causes a critical decrease in bone mineral density (BMD), an important determinant of fracture risk. During the premenopausal period, hypogonadism can have deleterious effects on skeletal health by reducing peak bone mass or inducing precocious bone loss. In young women, hypothalamic amenorrhea, caused by gonadotropin-releasing hormone pulsatility dysregulation, is often associated with bone loss. Although the relationship between hypothalamic amenorrhea and bone density is not completely understood, the most plausible intervention for this disorder at the moment seems to be the use of hormone replacement. Oral contraceptives are associated with an improvement in BMD if assumed upon the onset of anovulatory cycles and, therefore, estrogen deficiency, but confer no benefit in healthy women with normal ovarian function. In perimenopausal oligomenorrheic women, the use of oral contraceptives seems to have bone-sparing effects. In conclusion, the protective role of oral contraceptives on bone density is biologically plausible, since this treatment represents a replacement therapy with continuous exposure to exogenous estrogens.