The altitude itself helps the thyroid to function normally. For example, one study (Savourey, et al., 1998) showed an 18% increase in T3 at a high altitude, and mitochondria become more numerous and are more efficient at preventing lactic acid production, capillary leakiness, etc. -Ray Peat, PhD Eur J Appl Physiol Occup Physiol. 1998;77(1-2):37-43. Pre-adaptation, [...]
