Relationship of ovarian hormones to hypoxemia in women residents of 4,300 m

Abstract

Prevalence of excessive erythrocytosis, the main sign of chronic mountain sickness (CMS), is greater in postmenopausal Andean women than in premenopausal women. It is uncertain whether this greater prevalence is related to the decline in female hormones and ventilatory function after the occurrence of the menopause. To study this, we compared the physiological variables involved in the physiopathology of CMS [end-tidal CO(2) (PET(CO(2)), Torr) and end-tidal O(2) (PET(O(2)), Torr), arterial oxygen saturation (Sa(O(2)), %), and Hb concentration (g/dl)] and progesterone and estradiol levels between postmenopausal and premenopausal women, both in the luteal and follicular phases. Women residing in Cerro de Pasco (n = 33; 4,300 m) aged 26--62 yr were studied. Postmenopausal women compared with premenopausal women in the luteal phase had lower PET(O(2)) (48 +/- 4 vs. 53 +/- 2 Torr, P = 0.005) and Sa(O(2)) levels (82 +/- 12 vs. 88 +/- 12%, P < 0.005) and higher PET(CO(2)) (34 +/- 2 vs. 29 +/- 3 Torr, P = 0.005) and Hb concentration (19 +/- 1 vs. 14 +/- 2 g/dl, P < 0.005). In addition, plasma progesterone was negatively correlated with PET(CO(2)) and positively correlated with PET(O(2)) and Sa(O(2)). No clear relationship was found among the cycle phases between estradiol and the variables studied. In conclusion, our results reveal that, before menopause, there is better oxygenation and lower Hb levels in women long residing at altitude, and this is associated with higher levels of progesterone in the luteal phase of the cycle.

Life-long consequences of postnatal normoxia exposure in rats raised at high altitude

“…As previously reported by several studies in experimental conditions and in high-altitude human residents, HACont females had higher VT (although V E was not higher), lower Hct and Hb levels, and reduced RV hypertrophy compared with males (22,27,28,40). These effects are mainly related to ovarian steroids.…”

Impaired acclimatization to chronic hypoxia in adult male and female rats following neonatal hypoxia

“…Alternatively, estradiol decreases erythropoietin synthesis under hypoxic exposure (35), which may also contribute to lower hematological response during chronic hypoxia in females. This sex effect is also found in humans living at high altitude, and may explain why chronic mountain sickness is generally not observed in women before menopause (30,31). Several studies have reported that disruption of normal neonatal environment may lead to gender-specific long-term effects on the respiratory control system (6, 16, 32), and it was one of our objectives to test this hypothesis in the present study.…”

“…Accordingly, we used rats to test this hypothesis. Because sex-specific effects of chronic hypoxia in adults or in newborn rats have been reported previously (6,25,34), and because chronic mountain sickness is typically observed in adult men rather than in women (30,31), we tested the hypothesis that the effects of neonatal hypoxia on ventilatory acclimatization to hypoxia would be sex specific.…”

Serum testosterone levels and excessive erythrocytosis during the process of adaptation to high altitudes

“…49 Among other things, relative alveolar hypoventilation has been suggested to result from reduced circulating female sex steroid hormone concentrations. [50][51][52][53] All of these data suggest that high serum testosterone levels and/or low serum oestradiol levels may be participating in hypoventilation, which may result in erythrocytosis and CMS in high-altitude populations. Testosterone can contribute to hypoventilation during sleep.…”