The Impact of Estrogen vs Energy Status on Bone Balance and Bone Turnover Rate in Young Exercising Women

Open Access
Author:
Oneglia, Andrew Philip
Area of Honors:
Kinesiology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Mary Jane De Souza, Thesis Supervisor
  • Mary Jane De Souza, Honors Advisor
  • Jinger Gottschall, Faculty Reader
Keywords:
  • Energy
  • Estrogen
  • Female Athlete Triad
  • Bone Health
Abstract:
Energy and estrogen deficiencies are detrimental to bone health in exercising women, but the significance of each independently has not been extensively examined, as energy and estrogen deficiency often occur simultaneously. The purpose of this study was to assess markers of bone formation (procollagen type I N-terminal propeptide) and resorption (serum C-terminal telopeptides) utilized in mathematical models of bone turnover to quantify how energy and estrogen status relate to indices of bone formation, bone resorption, the net balance of bone formation and resorption (bone balance), and bone turnover rate in 109 physically active, premenopausal women (18-35 years old). Energy status was assessed using total triiodothyronine (TT3) concentration; estrogen status was assessed using self-reported history of menses verified by prospective assessments of urinary estrone-1-glucuronide (E1G) and pregnanediol glucuronide (PdG). Participants were categorized as energy replete (EnR) or energy deficient (EnD) and estrogen replete (E2R) or estrogen deficient (E2D), resulting in four subgroups: EnR+E2R (n=37), EnR+E2D (n=18), EnD+E2R (n=22) and EnD+E2D (n=32). All groups were similar with respect to height and weight (p>0.05). Energy deficiency was associated with suppressed TT3 concentrations (67.1±1.4 ng/dL, p<0.001), while estrogen deficiency was associated with decreased E1G and PdG integrated mean concentrations (27.4±2.0 ng/mL and 2.0±0.7 g/L, respectively, both p<0.001). EnD+E2D women had the lowest bone turnover rate (1.43±0.08, p=0.045) driven by a lower index of bone formation (MoMf) (1.00±0.06 g/L, p=0.046) compared to EnR+E2D women (1.98±0.16 and 1.44±0.14 g/L, respectively). Energy status impacted the index of bone resorption, such that EnD women had less bone resorption (1.01±0.05 ng/mL, p=0.019) than EnR women. There were no effects of estrogen or energy status on bone balance, yet values were indicative of net bone formation in all groups. Energy status was the main contributor to negative alterations in bone turnover dynamics, especially among estrogen deficient women, highlighting the importance of preventing energy deficiency among exercising women, especially those with menstrual disturbances, in order to maintain skeletal health.