Reply to Colburn and Stachenfeld.

Letter to the EditorReply to Colburn and StachenfeldCasey G. Turner, Anna E. Stanhewicz, Karen E. Nielsen, Jeffrey S. Otis, Rafaela G. Feresin, and Brett J. WongCasey G. TurnerDepartment of Kinesiology and Health, Georgia State University, Atlanta, Georgia, United StatesMolecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts, United States, Anna E. StanhewiczDepartment of Health and Human Physiology, University of Iowa, Iowa City, Iowa, United States, Karen E. NielsenDepartment of Population Health Sciences, School of Public Health, Georgia State University, Atlanta, Georgia, United States, Jeffrey S. OtisDepartment of Kinesiology and Health, Georgia State University, Atlanta, Georgia, United States, Rafaela G. FeresinDepartment of Nutrition, Georgia State University, Atlanta, Georgia, United States, and Brett J. WongDepartment of Kinesiology and Health, Georgia State University, Atlanta, Georgia, United StatesPublished Online:04 Aug 2023https://doi.org/10.1152/japplphysiol.00408.2023MoreSectionsPDF (246 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat to the editor: The Letter from Colburn and Stachenfeld (1) regarding our recent work assessing the effects of biological sex and oral contraceptive pill (OCP) use on cutaneous microvascular function emphasizes points to consider in research assessing sex differences and/or sex hormone effects on physiological outcomes.Colburn and Stachenfeld highlight that physiological research commonly uses different definitions to select samples of women, grouping subsets of women together or excluding hormonal exposures altogether, but this is often completed without justification for such experimental design choices. Our recent data suggest that it is important to consider and report exogenous hormonal exposure in physiological research unless justified otherwise. Importantly, our data (2) contest the idea that the placebo pill phase of OCP use is equivalent to the menstrual phase of the natural menstrual cycle (at least in our investigation of the nitric oxide component of submaximal endothelium-dependent vasodilation within the cutaneous microcirculation).Colburn and Stachenfeld also propose methodological suggestions for testing women in physiological research, such as including a washout period for women who use OCP. The post-OCP condition has been largely uninvestigated (3). A recent case study from our laboratory (4) showed an increase in endothelial function 20 mo after OCP cessation, but this single case does not provide insight into the generalizability of findings to other individuals or OCP formulations. Furthermore, the effect of OCP on molecular mechanisms is still under-investigated (3), so there is no clear indication if a washout period is necessary or how long it might need to be. Although considering and reporting the effects of these commonly used prescription medications is important, it is not our intent to discourage inclusion of these women in physiological research. The most pertinent perspective to consider may be whether external or internal validity is of utmost importance for a study’s aim.Our data demonstrate the importance of designing an experiment based on the primary outcome variable(s) of a study. In our study assessing the cutaneous microcirculation, naturally cycling women during the menstrual phase and men of similar age demonstrated significantly different overall endothelium-dependent vasodilation but seemingly equivalent nitric oxide-dependent vasodilation (2). Simultaneously, naturally cycling women and women using OCP had similar endothelium-dependent vasodilation, but different nitric oxide-dependent vasodilation, when tested in their respective low hormone phases (2). This may justify certain decisions for experimental design based on the primary outcome variable in question, but it is important to confirm our findings in women using OCP across other days of the placebo phase. Furthermore, our study highlights how inclusion of a more broadly defined sample of women, accompanied by planned sub-group analyses or stratifying participants (suggested by Colburn and Stachenfeld), may reveal both similarities and differences in physiological outcomes in distinct subsets of women.Women in general remain underrepresented in research, and there are also specific subsets of women or hormonal exposures even less represented but no less important to be considered. We thank Colburn and Stachenfeld for sharing their comments. We hope these conversations about endogenous and exogenous hormone exposures in physiological research continue.DISCLOSURESNo conflicts of interest, financial or otherwise, are declared by the authors.AUTHOR CONTRIBUTIONSC.G.T. drafted manuscript; C.G.T., A.E.S., K.E.N., J.S.O., R.G.F., and B.J.W. edited and revised manuscript; C.G.T., A.E.S., K.E.N., J.S.O., R.G.F., and B.J.W. approved final version of manuscript.REFERENCES1. Colburn AT, Stachenfeld NS. Comment on “Effects of biological sex and oral contraceptive pill use on cutaneous microvascular endothelial function and nitric oxide-dependent vasodilation in humans”. J Appl Physiol (1985). doi:10.1152/japplphysiol.00335.2023.Link | ISI | Google Scholar2. Turner C, Stanhewicz A, Nielsen K, Otis J, Feresin R, Wong B. Effects of biological sex and oral contraceptive pill use on cutaneous microvascular endothelial function and nitric oxide-dependent vasodilation in humans. J Appl Physiol (1985) 134: 858–867, 2023. doi:10.1152/japplphysiol.00586.2022. Link | ISI | Google Scholar3. Williams J, MacDonald M. Influence of hormonal contraceptives on peripheral vascular function and structure in premenopausal females: a review. Am J Physiol Heart Circ Physiol 320: H77–H89, 2021. doi:10.1152/ajpheart.00614.2020. Link | ISI | Google Scholar4. Turner C, Stanhewicz A, Nielsen K, Wong B. Microvascular endothelial function following cessation of long-term oral contraceptive pill use: a case report. Exp Physiol 108: 5–11, 2023. doi:10.1113/EP090861. Crossref | PubMed | ISI | Google ScholarAUTHOR NOTESCorrespondence: C. G. Turner (casey.turner@tuftsmedicine.org). Download PDF Previous Back to Top FiguresReferencesRelatedInformation Related ArticlesComment on “Effects of biological sex and oral contraceptive pill use on cutaneous microvascular endothelial function and nitric oxide-dependent vasodilation in humans” 04 Aug 2023Journal of Applied Physiology More from this issue > Volume 135Issue 2August 2023Pages 487-488 Crossmarkhttps://doi.org/10.1152/japplphysiol.00408.2023PubMed37541851History Received 26 June 2023 Accepted 26 June 2023 Published online 4 August 2023 Published in print 1 August 2023 Keywordsendothelial functionmicrovascular functionnitric oxideoral contraceptiveswomen’s health Metrics