Endocrine Abstracts

Background: Arginine vasopressin (AVP) changes during altitude acclimatization is of clinical interest as increases in their plasma levels (with reference to sea-level (SL)) have been associated with fluid retention accompanied by elevated plasma cortisol levels. Studies have reported no change/ decrease in plasma AVP during ‘normal’ acclimatization. This study was conducted to evaluate plasma AVP changes and the associated physiological changes during chronic exposure to high-altitude (HA).

Methods: Healthy, male volunteers (n=36) between 20–50 years of age were recruited for the study. Subjects were evaluated both at SL and HA (4500 m, 3–4 weeks of stay) for the following parameters: plasma cortisol (CORT) and AVP (ELISA), haemoglobin(Hb), hematocrit(Hct), plasma sodium (Na); total protein (PROT), body weight (BW), arterial oxygen saturation (SaO₂), heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP). Values are mean±S.D.

Results: At HA, all subjects were asymptomatic and exhibited physiological characteristics of altitude acclimatization (↓: BW, SaO₂; ↑: Hb, Hct, MAP, HR; ↔: RR). Plasma AVP and CORT level during HA exposure was within ‘SL normal range’. Subjects were categorized as follows:

Conclusions: Altitude acclimatization is characterised by physiological variation in both plasma AVP and CORT levels. However, the significance of ‘subtle’ changes in AVP with regard to body fluid regulation (re-setting of osmotic threshold) needs further evaluation.