Females, Aging, Metabolism, and Exercise

Participants will be women who are nearing menopause based on age (42-52 y) but have normal menstrual cycles. Participants will be randomized to receive monthly injections of placebo or a study drug that reduces sex hormones (GnRH agonist) for 24 weeks. Women who receive GnRH agonist will be further randomized to no exercise or a supervised exercise program. Thus, the 3 treatment groups are: placebo, GnRH agonist, GnRH agonist+exercise. The investigators will measure changes in calories burned during physical activity, sleep, rest, and after a meal after 3 and 6 months of hormone suppression using doubly-labeled water and room calorimetry. Other measures include food intake estimated from food records; body composition measured by dual-energy x-ray absorptiometry (DXA); glucose and insulin responses to an oral glucose tolerance test; and markers of inflammation in the blood.

Inclusion criteria

• Healthy women aged 40 to 60 years
• Are still experiencing regular menstrual cycles.
• They must be willing to be randomized to placebo or GnRHAG therapy for 24 weeks
• Be physically able to be randomized to participate in a programmed exercise training program.

The investigators will consent up to 132 subjects with the aim of enrolling 22 in each of the 3 groups (placebo, GnRHAG, or GnRHAG+Exercise).

Exclusion criteria

• irregular menstrual cycles defined as 2 or more missed cycles in the previous year
• serum FSH >25 mIU/mL measured during the first 5 days of the menstrual cycle
• on hormonal contraceptive or menopausal therapy
• positive pregnancy test
• intention to become pregnant or start hormonal contraceptive therapy during the period of study
• lactation
• known hypersensitivity to GnRH or leuprolide acetate
• score >16 on the CESD((Center for Epidemiologic Studies Depression Scale )
• severe osteopenia or osteoporosis (i.e., proximal femur or lumbar spine t scores < -2.0)
• abnormal vaginal bleeding
• thyroid dysfunction, defined as an ultrasensitive TSH <0.5 or >5.0 mU/L; volunteers with abnormal TSH values will be re-considered for participation in the study after follow-up evaluation by the PCP with initiation or adjustment of thyroid hormone replacement
• uncontrolled hypertension defined as resting systolic BP >150 mmHg or diastolic BP>90 mmHg; participants who do not meet these criteria at first screening will be re-evaluated, including after follow-up evaluation by the PCP with initiation or adjustment of anti-hypertensive medications
• cardiovascular disease; subjective or objective indicators of ischemic heart disease (e.g., angina, ST segment depression) or serious arrhythmias at rest or during the graded exercise test (GXT) without follow-up evaluation; follow-up evaluation must include diagnostic testing (e.g., thallium stress test) with interpretation by a cardiologist
• orthopedic or other problems that would interfere with participation in the exercise program
• exercising at least 30 minutes per day at a moderate to vigorous intensity most days of the week (defined as >4 d/wk) over the past 6 months
• BMI <40 kg/m2