This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Oral contraceptives generally suppress endogenous production of estrogen, so a more clinically important issue in adolescents is what dose of estrogen is associated with optimal bone growth and mineralization. The purpose of this new pilot study is to compare bone mineral density over two years in 60 adolescents girls, aged 12 - 18 years, who choose oral contraceptives for birth control. They will be randomized to receive either Loestrin (20 mcg ethinyl estradiol, 0.1 mg norethidrone) or Ortho 1/35. Bone mineral density results will also be compared with those from a non-hormonal control group recruited concurrently from the same clinic sites. Eligible subjects will undergo the routine procedure for initiating hormonal contraception, including a brief physical and (usually) a pelvic examination. A semi-annual outpatient visit in the GCRC for measurement of bone mineral density by DEXA, anthropometric measurements for body composition and complete a self-report calcium intake and exercise questionnaire. Blood and urine samples will be obtained to assess vitamin D, circulating levels of estradiol plus biochemical markers of bone metabolism.
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