biostudies-literatureUnknown5Castellanos-Mendoza MC<h4>Introduction</h4>The release of luteinising hormone (LH) before ovulation is disrupted during a state of low energy availability (EA). However, it remains unknown whether a threshold EA exists in athletic populations to trigger ovulatory disturbances (anovulation and luteal phase deficiency) as indicated by peak/mid-luteal serum progesterone concentration (Pk-PRG) during the menstrual cycle.<h4>Methods</h4>We assessed EA and Pk-PRG in 15 menstrual cycles to investigate the relationship between EA and Pk-PRG in free-living, competitive (trained-elite) Guatemalan racewalkers (<i>n </i>= 8) and runners (<i>n </i>= 7) [aged: 20 (14-41) years; post-menarche: 5 (2-26) years; height: 1.53 ± 0.09 m; mass: 49 ± 6 kg (41 ± 5 kg fat-free mass "FFM")]. EA was estimated over 7 consecutive days within the follicular phase using food, training, and physical activity diaries. A fasted blood sample was collected during the Pk-PRG period, 6-8 days after the LH peak, but before the final 2 days of each cycle. Serum progesterone concentration was quantified using electrochemiluminescence immunoassay.<h4>Results</h4>Participants that reported an EA of <35 kcal·kg FFM^-1·day^-1 (<i>n </i>= 7) exhibited ovulatory disturbances (Pk-PRG ≤9.40 ng·mL^-1). Athletes with EA ≥36 kcal·kg FFM^-1·day^-1 (<i>n </i>= 8) recorded "normal"/"potentially fertile" cycles (Pk-PRG >9.40 ng·mL^-1), except for a single racewalker with the lowest reported protein intake (1.1 g·kg body mass^-1·day^-1). EA was positively associated with Pk-PRG [<i>r</i>(9) = 0.79, 95% confidence interval (CI): 0.37-0.94; <i>p </i>= 0.003; 1 - <i>β</i> = 0.99] after excluding participants (<i>n </i>= 4) that likely under-reported/reduced their dietary intake.<h4>Conclusions</h4>The result from the linear regression analysis suggests that an EA ≥ 36 kcal·kg FFM^-1·day^-1 is required to achieve "normal ovulation." The threshold EA associated with ovulatory disturbances in athletes and non-invasive means of monitoring the ovulatory status warrant further research.Frontiers in sports and active living1279534https://www.ebi.ac.uk/biostudies/studies/S-EPMC10690956biostudies-literatureFree-living competitive racewalkers and runners with energy availability estimates of <35 kcal·kg fat-free mass^-1·day^-1 exhibit peak serum progesterone concentrations indicative of ovulatory disturbances: a pilot study.PMC10690956Galloway SDRCastellanos-Mendoza MCWitard OCfalseFree-living competitive racewalkers and runners with energy availability estimates of <35 kcal·kg fat-free mass^-1·day^-1 exhibit peak serum progesterone concentrations indicative of ovulatory disturbances: a pilot study.<h4>Introduction</h4>The release of luteinising hormone (LH) before ovulation is disrupted during a state of low energy availability (EA). However, it remains unknown whether a threshold EA exists in athletic populations to trigger ovulatory disturbances (anovulation and luteal phase deficiency) as indicated by peak/mid-luteal serum progesterone concentration (Pk-PRG) during the menstrual cycle.<h4>Methods</h4>We assessed EA and Pk-PRG in 15 menstrual cycles to investigate the relationship between EA and Pk-PRG in free-living, competitive (trained-elite) Guatemalan racewalkers (<i>n </i>= 8) and runners (<i>n </i>= 7) [aged: 20 (14-41) years; post-menarche: 5 (2-26) years; height: 1.53 ± 0.09 m; mass: 49 ± 6 kg (41 ± 5 kg fat-free mass "FFM")]. EA was estimated over 7 consecutive days within the follicular phase using food, training, and physical activity diaries. A fasted blood sample was collected during the Pk-PRG period, 6-8 days after the LH peak, but before the final 2 days of each cycle. Serum progesterone concentration was quantified using electrochemiluminescence immunoassay.<h4>Results</h4>Participants that reported an EA of <35 kcal·kg FFM^-1·day^-1 (<i>n </i>= 7) exhibited ovulatory disturbances (Pk-PRG ≤9.40 ng·mL^-1). Athletes with EA ≥36 kcal·kg FFM^-1·day^-1 (<i>n </i>= 8) recorded "normal"/"potentially fertile" cycles (Pk-PRG >9.40 ng·mL^-1), except for a single racewalker with the lowest reported protein intake (1.1 g·kg body mass^-1·day^-1). EA was positively associated with Pk-PRG [<i>r</i>(9) = 0.79, 95% confidence interval (CI): 0.37-0.94; <i>p </i>= 0.003; 1 - <i>β</i> = 0.99] after excluding participants (<i>n </i>= 4) that likely under-reported/reduced their dietary intake.<h4>Conclusions</h4>The result from the linear regression analysis suggests that an EA ≥ 36 kcal·kg FFM^-1·day^-1 is required to achieve "normal ovulation." The threshold EA associated with ovulatory disturbances in athletes and non-invasive means of monitoring the ovulatory status warrant further research.2023-01-01T00:00:00Z20232026-06-03T08:05:46.051Z2026-04-26T03:11:17.973ZS-EPMC106909563804693210.3389/fspor.2023.1279534