Impaired Endothelium-Dependent and -Independent Vasodilation in Young Female Athletes With Exercise-Associated Amenorrhea

Abstract

To the Editor: Estrogen has great roles in controlling vascular function.1 Especially, estrogen augments endothelium-dependent vasodilation by increasing the bioavailability of endothelium-derived nitric oxide.2 Not only does estrogen replacement improve endothelium-dependent vasodilation in postmenopausal women,3 but also endothelium-dependent vasodilation is enhanced by endogenous estradiol during the menstrual cycle in women.4 Exercise-associated amenorrhea (EAA) is observed in highly-trained female athletes.5 Although physical exercise training usually improves vascular function in subjects with cardiovascular risk factors,6 it is unknown whether such strenuous sport activity that causes amenorrhea affects vascular function. Flow-mediated vasodilation (FMD) during reactive hyperemia can be quantitated as an index of endothelium-dependent vascular function.7 FMD was shown to be reduced in amenorrheic athletes,8 however it was unclear whether the abnormality of FMD was related to estrogen levels. Accordingly, we investigated vascular function in young highly trained athletes with and without EAA, and measured endogenous ovarian hormones to explore the underlying mechanisms of endothelial dysfunction in amenorrheic athletes. We also examined whether vascular function was restored by the recovery of the regular menstrual cycle after quitting competitive sport activity. We enrolled 26 young female highly-trained volleyball players (mean age, 16.4 years) including athletes with a regular menstrual cycle (RMC; n=14) and those with EAA (n=12). Age-matched female non-athletes with a regular menstrual cycle were enrolled as controls (n=10). The players participated regularly in exercise training 6 days a week and …