Effects of Oral vs. Non-oral Contraceptives on the GH/IGF-1 Axis

This study is a preclinical, multi-site trial (Penn State University and Purdue University) that will determine whether the negative effects of combined oral contraceptive (COC) therapy on bone turnover are dependent on the route of administration such that an attenuation of these effects is observed when a comparable dose of non-oral transdermal contraceptive (TDC) therapy and contraceptive vaginal ring (CVR) therapy are also tested. Millions of women use COC therapy for birth control purposes or regulation of menstrual cycles. TDC and CVR therapies are relatively new FDA-approved contraceptive alternatives to COC. The purpose of the proposed project is to address the potential mechanism(s) by which oral ethinyl estradiol (EE) may negatively impair bone via "first pass" effects on the liver and compare these effects to transdermally-administered and vaginally-administered EE in young women. We will assess mechanistic effects by way of 2-day serial sampling and by an insulin-like growth factor (IGF-1) generation test. The IGF-1 generation test was developed over 20 years ago and is currently used to diagnose growth hormone (GH) insensitivity. IGF-1 generation tests may also be used to amplify effects not observable by the assessment of fasting or serial concentrations of systemic IGF-1(secreted by the liver) and its associated binding proteins. This study will be the first study to examine the physiological mechanisms whereby the route of estrogen administration affects the GH/IGF-1 axis and bone turnover in young women.

The overall purpose of this study is to explore differences in liver metabolism and bone turnover of oral versus transdermal and vaginal contraceptive therapy. In an effort to expose the route-dependent effects of oral versus transdermal and vaginal contraceptive therapy on liver and bone metabolism, we will examine the effects of ethinyl estradiol on serially-assessed fasting concentrations of the GH/IGF-1 axis and bone turnover and explore physiological mechanisms underlying hepatic responsiveness to oral versus transdermal and vaginal contraceptive therapy using an IGF-1 Generation Test as a probe.

Inclusion criteria

• Female
• Age 18-30 yrs
• BMI 18-29 kg/m2
• Non-smoking
• Not using hormonal contraceptives for at least 6 months prior
• Not currently pregnant nor intending to become pregnant in the next 6 months
• Not lactating
• No apparent metabolic, endocrine, musculoskeletal, or severe psychiatric disease
• Willing to adhere to maintenance of current exercise training and diet and remain weight stable (±2 kg) during study
• Variable physical activity acceptable, but mode must be primarily weight bearing
• At least 9 menses in past 12 months
• Willing to quit taking any current nutritional supplements and take Calcium and Vitamin D supplements for the duration of the study.
• If 21 or older, a normal Pap smear must be confirmed.

Exclusion criteria

• Non-weight bearing exercise as primary mode of physical activity
• Known or suspected metabolic or endocrine disease
• Pregnant
• Currently consuming large amounts of soy products
• Regular consumption of grapefruit juice
• Current clinical eating disorder or other axis 1 psychiatric or bipolar disorders
• Oral or hormonal contraceptive use in the last 6 months
• Currently amenorrheic
• Hyperparathyroidism
• Liver or renal disease
• Evidence of malabsorption or skeletal disorder
• Thyroid abnormalities (controlled hypothyroidism acceptable)
• Chronic use of non-steroidal anti-inflammatory drugs (NSAIDS)
• Taking medications known to have interactions with contraceptive therapy
• Division I Athlete, on or off season
• Other Exclusion Criteria proposed by the World Health Organization COC Contraindications (Grossman, 2011)