Regular exercise is an essential component of prevention of obesity, but in adolescent young women, physical conditioning is associated to multiple endocrine aberrations and an increased risk of fractures. High-intensity exercise activates the hypothalamic-pituitary-adrenal axis (HPA), increases cortisol concentration, disrupts the menstrual cycle, and can lead to premature osteoporosis. In athletes, menstrual cyce disruption reflects decreased activity of the hypoyhalamic-pituitary -gonadal axis (HPG). Decreased bone mass is particularly alarming for adolescent young women as bone accretion reaches a plateau in the post-pubertal years, thereby rendering them vulnerable to life-long increased risk of osteporosis. There is a need to identify reliable predictors for exercise-induced amenorrhea in adolescents of normal weight. Cortisol is increased in athletes and studies in other populations have shown that an endogenous increase in cortisol is linked to bone loss. The proposed project will test the hypothesis that the activation of the HPA axis is a preditor of subsequent decrease of HPG activity and estrogen concentrations thereby increasing the risk of osteoporosis in active post-pubertal girls. We plan to conduct an intervention study on adolescent girls of 14 to 16 years of age and preparing for team sports or enrolling in a supervised training program. The study will be framed by the periods of on and off training as they are imposed in high schools. Cardiovascular fitness will be assessed by maximal oxygen consumption (VO2max) and outcomes of interest will be 24-hour cortisol concentrations, gonadotropins and bone density, as well as changes in body composition, leptin and insulin sensitivity. Our goal will be to identify early markers of declining gonadotropin function and bone health in postpubertal young women as they improve cardiovascular capacity

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Mentored Patient-Oriented Research Career Development Award (K23)
Project #
5K23DK065995-02
Application #
6914914
Study Section
Diabetes, Endocrinology and Metabolic Diseases B Subcommittee (DDK)
Program Officer
Hyde, James F
Project Start
2004-07-01
Project End
2008-06-30
Budget Start
2005-07-01
Budget End
2006-06-30
Support Year
2
Fiscal Year
2005
Total Cost
$157,359
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Pediatrics
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Kasa-Vubu, Josephine Z; Jain, Vandana; Welch, Kathy (2010) Impact of fatness, insulin, and gynecological age on luteinizing hormone secretory dynamics in adolescent females. Fertil Steril 94:221-9
Singer, K; Rosenthal, A; Kasa-Vubu, Josephine Z (2009) Elevated testosterone and hypergonadotropism in active adolescents of normal weight with oligomenorrhea. J Pediatr Adolesc Gynecol 22:323-7
Watkins, Mark G; Clark, Kathryn M; Foster, Carol M et al. (2007) Relationships among body mass index, parental perceptions, birthweight and parental weight after referral to a weight clinic. J Natl Med Assoc 99:908-13
Kasa-Vubu, J Z; Rosenthal, A; Murdock, E G et al. (2007) Impact of fatness, fitness, and ethnicity on the relationship of nocturnal ghrelin to 24-hour luteinizing hormone concentrations in adolescent girls. J Clin Endocrinol Metab 92:3246-52
Foster, Carol M; Barkan, Ariel; Kasa-Vubu, Josephine Z et al. (2007) Ghrelin concentrations reflect body mass index rather than feeding status in obese girls. Pediatr Res 62:731-4
Kasa-Vubu, J Z; Ye, W; Borer, K T et al. (2006) Twenty-four hour growth hormone and leptin secretion in active postpubertal adolescent girls: impact of fitness, fatness, and age at menarche. J Clin Endocrinol Metab 91:3935-40
Kasa-Vubu, Josephine Z; Dimaraki, Eleni V; Young, Elizabeth A (2005) The pattern of growth hormone secretion during the menstrual cycle in normal and depressed women. Clin Endocrinol (Oxf) 62:656-60