Hormonal changes in normal and polycythemic high-altitude natives

Abstract

Acute and chronic exposure to high-altitude (HA) hypoxia inhibits the renin-angiotensin-aldosterone system and may modify the release of atrial natriuretic peptide (ANP) in sea-level (SL) natives. In HA natives, the release of these hormones could be influenced by changes in blood volume or pulmonary arterial pressure. Twenty-four men residing in La Paz, Bolivia, at 3,600 m were separated into two groups: one normocythemic (HAN; with hematocrit < 57%; n = 13) and the other polycythemic (HAP; with hematocrit > 57%; n = 11). A control group of 9 SL residents was studied in normoxia (SLN) as well as after 4 days spent at 4,350 m (SLH). The groups were tested for plasma active renin (PAR), plasma aldosterone concentration, ANP, and potassium and norepineprine concentrations at rest and after a maximal exercise. Pulmonary arterial systolic pressure was assessed by a Doppler technique. It was observed that PAR and plasma aldosterone concentration at rest and after exercise were lower in the SLH than in the SLN group. PAR and norepineprine concentration were higher among highlanders than in the SLN group. Renin response to exercise was normal among the HAN group and slightly decreased among the HAP group, and an exercise-induced increase in aldosterone was attenuated in both HA groups. Aldosterone response to renin was maintained among the SLH group but was attenuated in the HA groups, possibly owing to a protective mechanism against salt and water retention. Resting and exercise ANP was lower in the HA groups than in the SLN group.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid baroreflex regulation of vascular resistance in high‐altitude Andean natives with and without chronic mountain sickness

“…It is likely that there would have been a greater sympathetic activation in the more hypoxaemic CMS patients, and this may have contributed to the altered carotid baroreflex function. This hypothesis is supported by the observation that resting noradrenaline and adrenaline levels are greater in CMS patients than in HA normal subjects (Antezena et al 1995), suggesting greater levels of sympathetic activity.…”

Differences in Cardiovascular and Hypothalamic-Pituitary-Adrenal Axis Functions between High-Altitude Visitors and Natives during a Trek on the Annapurna Circuit

“…However, the available information on HPA axis function in Sherpas or other lineages that have adapted to HA living is limited. Previous studies have observed a blunted sympathoneural response to hypobaric hypoxemia in HA natives of Bolivia and the Andes [45,46] and a blunt ACTH and cortisol response to exogenous CRH in HA natives of Andes [47]. Thus, the distinctive physical and physiological characteristics of HA natives are possible explanations for the observed differences in HPA axis and cardiovascular function between Sherpas and trekkers during the trek on the Annapurna circuit.…”

Reduction of subcutaneous mass, but not lean mass, in normal fetuses in Denver, Colorado

“…A number of human and animal studies have shown that high altitude exposure and its associated relative hypoxia induce changes in the hematologic and hemodynamic profiles of adults and fetuses. [1][2][3][4][5][6][7] Human studies showing a decrease in birth weight at high altitude have been performed in Leadville, Colo (altitude, 3100 m) and in Tibet (altitude, 3658 m). [8][9] Reduced birth weight has also been reported at moderately high altitude (Denver, 1600 m) compared with sea level.…”