Acute Mountain Sickness Is Associated With a High Ratio of Endogenous Testosterone to Estradiol After High-Altitude Exposure at 3,700 m in Young Chinese Men

Abstract

Background: A large proportion of populations suffer from acute mountain sickness (AMS) after exposure at high altitude. AMS is closely related with age and gender implying that the sex hormones may play critical roles in AMS. Our observational study aimed to identify the association between the endogenous testosterone (T), estradiol (E2) and AMS. Methods: A total of 113 subjects were recruited in 2012. The participants were evaluated at 500 m and after acute (1 day) and short-term (7 days) high-altitude exposure at 3,700 m. The subjects also completed a case report form questionnaire and underwent blood pressure measurements and an echocardiography examination. The red blood cell (RBC) count, Hb concentration ([Hb]), hematocrit (HCT), E2, T, and erythropoietin (EPO) were measured. Results: Upon acute high-altitude exposure, E2 and EPO were significantly lower in AMS⁺ group, and T/E2 and stroke volume were higher. On the 1st day, AMS score correlated positively with the T/E2 ratio while it negatively correlated with E2. After 7 days at 3,700 m, the AMS⁺ subjects had higher erythropoietic parameters: EPO, T, and T/E2 were significantly higher in the AMS⁺ group. [Hb], RBC count, HCT, EPO, T and T/E2 were also correlated with AMS score. EPO, HCT, and the RBC count were also correlated with T/E2. Regression analyses indicated that T/E2 significantly correlated to AMS score and T/E2 on the 1st day was an independent predictor for AMS on the 7th day. Conclusion: AMS was correlated with T/E2 ratio and EPO. After short-term exposure, higher T/E2 may contribute to AMS together with EPO via erythropoiesis. Furthermore, T/E2 level at high altitude in the early stage was an independent predictor for AMS in the latter stage.

Keywords: acute mountain sickness; erythropoiesis; estradiol; high-altitude exposure; testosterone.

FIGURE 1

The flow chart of this study.

FIGURE 2

Modifications of sex hormones, EPO and hematopoiesis after high-altitude exposure. Compared with baseline: ^∗p is 0.05 or less; ^∗∗p is 0.01 or less. Compared with 24-h level: ⁺p is 0.05 or less; ⁺⁺p is 0.01 or less. (A) Modification of SpO₂; (B) Change of HR; (C) Modification of [Hb]; (D) Change of HCT; (E) Change of EBC count; (F) Change of EPO; (G) Change of E2; (H) Change of T; (I) Change of T/E2; (J) Change of EF; (K) Change of SV; (L) Change of CIn; (M) Change of SV after high altitude exposure; (N) Change of CO after high altitude exposure; and (O) Change of CIn after high altitude exposure.

FIGURE 3

The potential mechanisms of sex hormones in AMS during different exposure durations. T and E2 may play various roles in AMS through different pathophysiological processes in a time dependent way.