Downregulation of bone remodelling during low dosage of oral contraception

Background: Epidemiological research discusses an enlarged risk of fractures under oral contraception. With this background on mind we wanted to examine bone mass, bone markers and hormonal regulation under low dose contraception. Methods: Controlled open study over a period of 2 years with a group of 50 women (25-35 years). After a period of OC-restriction for at least four months 25 women decided to take OC (30 mu g Ethinylestradiol and 75 mu g Gestoden), the other 25 women formed the control group. At the start of the study, after 6 and after 24 month the serum levels of bone markers (BAP, BGP, DPD, PYD) were measured. At the beginning and at the end the bone mass of the lumbar spine an of the neck of the femur was measured by DEXA (SOPHOS). Results: Downregulation of the pituitary-gonadal feedback mechanism and a significant decrease of the bone markers BGP, PYD after 6 months OC intake. Permanence of trabecular and cortical bone mass in both groups. Conclusions: In this age group the results can be seen in the sense of a reduced bone remodelling. As a cause a reduced activity of the transformation units of osteoblasts can be assumed.