Bone mass and long-term monophasic oral contraceptive treatment in young women

A prospective study has been designed to investigate bone metabolism in young women taking an oral monophasic contraceptive formulation (ethinylestradiol 20 micrograms + desogestrel 0.150 mg) over 5 years. Healthy women (n = 200) between 19 and 22 years of age were divided into two groups. Group A received oral contraception, Group B did not receive any treatment. All the subjects underwent a bone mass density (BMD) evaluation at spinal level L2-L4 with Dexa (Norland XR-26) and a measurement of the serum alkaline phosphatase levels and urinary excretion of OH-proline at baseline and every 12 months over 5 years. Our results demonstrated that Group A did not show any significant BMD change after 5 years of oral contraceptive treatment, while Group B demonstrated a significant increase (p < 0.01) in the bone mass content at the end of the time of observation (+7.8% after 5 years). No significant changes were found in serum alkaline phosphatase levels and in urinary excretion of OH-proline at the end of the study in comparison with basal levels in both groups. Our data suggested that long-term treatment with an oral monophasic contraceptive formulation (ethinylestradiol 20 micrograms + desogestrel 0.150 mg) did not modify the BMD but prevented the occurrence of the physiologic peak of bone mass in young women.