"In order to compensate for the low partial pressure of oxygen at altitude, the human body undergoes a number of physiological changes. A vital component in this process is the increase in the concentration of circulating hemoglobin. The role of HIF-1alpha, erythropoietin and red blood cells in this acclimatization process is described, together with the fall in plasma volume that increases the concentration of hemoglobin in the early stages of hypoxic exposure."
Difference between these people and men on TRT: We have increased blood volume and hemoglobin/hematocrit.
Full paper: Heights and haematology: the story of haemoglobin at altitude
Prevalence, Clinical Profile, Iron Status, and Subject-Specific Traits for Excessive Erythrocytosis in Andean Adults Living Permanently at 3,825 Meters Above Sea Level
"We found a lower prevalence of high red blood cells than in previous reports in the Peruvian Andes. Although the presence of hypoxemia and decreased vital capacity were strongly associated with excessive erythrocytosis, being overweight or having metabolic syndrome were associated with an important fraction of cases in our study population."
Lack of Prominent Compensatory Polycythemia in Traditional Native Andeans Living at 4,200 Meters
Abstract
Red blood cell count (RBC), hemoglobin concentration ([Hb]) and hematocrit (Hct) were measured in 303 male Quechua children and adults, aged 6 to 57 years, living a lifestyle as traditional pastoralists and horticulturalists at a mean altitude of 4,200 m in the Southern Peruvian Andes. Values for RBC, [Hb], and Hct increased with age from middle childhood to young adulthood. However, among adults there was no significant association between age and any of these three parameters. Overall, there was approximately a 10-12% increase in the RBC, [Hb], and Hct above sea-level norms for all age groups. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) showed a slight but significant increase with age in children and adolescents, but the mean corpuscular hemoglobin concentration (MCHC) did not. We conclude that the study of highland Quechua Indians, living a traditional lifestyle as pastoralists and horticulturalists, does not support the long-held belief that altitude hypoxia provokes a dramatic compensatory polycythemia in healthy Andeans.