 This is exacerbated by other stressors such as undernutrition and lack of sleep, such as in a military training setting.During endurance exercise, before exhaustion, there may be elevated thyroid hormone levels due to increased expected energy demand (type 2 allostatic load).Cold exposure and stay at high altitude may lead to type 1 or type 2 phenotype, depending on duration and other boundary conditions (which determine whether or not stress is associated with energy deprivation).