Energy availability and sex steroid hormones in physically active females
- UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
- Samantha J. Goldenstein (Creator)
- Institution
- The University of North Carolina at Greensboro (UNCG )
- Web Site: http://library.uncg.edu/
- Advisor
- Laurie Wideman
Abstract: Sex steroid hormones (i.e., estrogen, progesterone) are major determinants of a women’s health status and play a role in almost every physiological system, including reproductive, endocrine, urinary, nervous, immune, musculoskeletal and cardiovascular. Physically active females have lower estrogen and progesterone when compared to inactive individuals, yet exercise alone does not appear to decrease hormones but alters hormones as a component of energy availability. Energy availability is the amount of energy left after subtracting the energy cost of exercise relative to fat free mass (FFM) from energy intake. When energy availability is inadequate (i.e., low energy availability (LEA)), disruptions to hormonal and metabolic systems occur that can lead to performance decrements and serious psychological and physiological (i.e., menstrual dysfunction) health outcomes. Furthermore, stress can disrupt estrogen and progesterone but how stress affects the relationship between energy availability and sex steroid hormones is unknown. Most research surrounding this topic includes only highly competitive, elite level female athletes and little is known about how energy availability alters hormone levels in physically active females. Since low sex steroid hormone concentrations and LEA are associated with serious health risks, further investigation into the association of energy availability and menstrual cycle hormones in physically active females is warranted. Thus, the purpose of this dissertation was to examine the relationship between energy availability and sex steroid hormones in active females across the menstrual cycle. Healthy, exercising females (n=21; age 21.3 ± 3.1 years) not on oral contraceptives completed measures over two menstrual cycles. Daily saliva measurements were taken across both menstrual cycles to create hormonal profiles of estrogen and progesterone. Energy availability was measured twice within one menstrual cycle, with energy intake recorded for seven days at two timepoints. Participants were all physically active and were asked to continue exercising normally and to record all exercise with a heart rate monitor. The first timepoint (T1) started during menses between day (D) 2-4 and the second timepoint (T2) started between 5-8 days post ovulation. A laboratory visit occurred on the first day of each timepoint, where resting metabolic rate and body composition were measured. Stress was measured with the Acute Recovery and Stress Scale at the beginning and end of each timepoint. Area under the curve (AUC) and range (i.e., difference in minimum and maximum values) for estrogen and progesterone for T1 and T2 was used for analyses. Most of the active females (71%, n = 15) were in a reduced energy state and 23% (n = 6) had subclinical menstrual dysfunction. Energy intake and energy availability remained constant across the two timepoints despite that estrogen and progesterone were significantly different (p = .003, p = .001, respectively). When the components of energy availability and hormones were assessed, progesterone range was positively associated with FFM (T1 p = .015, r=.537; T2 p = .001, r = .674) and RMR (T2 p = .005, r = .605) yet T2 progesterone range, FFM, and RMR were all negatively associated with energy availability (p = .032, r = -.479; p = .001, r = -.672; p = .009, r = -.558). Energy intake was correlated with the progesterone to estrogen ratio (P:E2) (p = .026, r= .321, 95% CI [0.04, 0.55]), but not progesterone or estrogen alone. The results also demonstrated that estrogen, progesterone, and the estrogen progesterone product in T1 exhibited a negative relationship with T2 energy availability ((ß = -.36, p = .009; ß = -.37, p = .008; ß = -.31, p = .029), in active females across a single menstrual cycle. In addition, stress and recovery do not moderate the relationship between hormones and energy availability within a timepoint or across timepoints of one menstrual cycle even though a stress subscale, negative emotional state, was significantly higher post ovulation towards the end of the cycle while recovery and other stress scales remained constant (F (3, 54) = 7.07, p = .000). These data suggest that physically active females are at risk for inadequate energy availability and subclinical menstrual dysfunction. Estrogen and progesterone affect energy intake at the beginning of the cycle and energy availability across timepoints but do not appear to be altered by stress and recovery. A higher progesterone to estrogen ratio was associated with higher energy intake during T1. Furthermore, higher estrogen and progesterone at the beginning of the menstrual cycle are associated with lower energy availability post ovulation. These data highlight the importance of including physically active females in future research on energy availability and emphasizes issues with energy availability are present in physically active females, not just elite athletes. Further investigations are needed to fully elucidate the relationship between energy availability, estrogen and progesterone.
Energy availability and sex steroid hormones in physically active females
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Created on 8/1/2023
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Additional Information
- Publication
- Dissertation
- Language: English
- Date: 2023
- Keywords
- Energy availability, Energy intake, Estrogen, Exercise, Menstrual cycle, Progesterone
- Subjects
- Exercise $x Physiological aspects
- Women $x Health and hygiene
- Steroid hormones
- Hormones, Sex
- Menstrual cycle