HPT‐ Axis Activation During Cold Head Out Water Immersion is Not Modified by Moderate Hypoxia
Abstract
The Bajau, an indigenous population renowned for breath‐hold diving, have comparatively large spleen volumes. This adaptation is purportedly indicative of a greater capacity to store red blood cells, which may aid operations in the aquatic environment. Spleen size in the Bajau is associated with the PDE10A genotype that encodes an enzyme that catalyzes the release of thyroxine (T4) from the thyroid gland. T4 is readily released during cold stress as the terminus to activation of the hypothalamus‐pituitary‐thyroid (HPT) ‐axis to increase metabolic rate. T4, and downstream counterpart triiodothyronine (T3), can also stimulate erythropoiesis by increasing erythropoietin production, which can be further promoted with hypoxia. Thus, exposure to cold water may augment erythropoiesis as hypoxia develops during breath‐hold diving via activation of the HPT‐axis. However, interactions between cold exposure and hypoxia on HPT‐axis activation have not been directly explored. Mountaineering expedition studies indirectly suggest that T4 release is elevated by hypoxia. Thus, this study tested the hypothesis that during cold head out water immersion (HOWI) acute hypoxia augments circulating thyroid hormone concentrations compared to normoxia.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- May 01, 2022
- Source ID
- 10.1096/fasebj.2022.36.s1.r4971
Entities
People
- Blair D Johnson
- Curtis S. Goss
- Jasosn M. Keeler
- Joel T. Greenshields
- Richara T. Logan
- Robert F. Chapman
- Tyler B. Baker
- Zachary J Schlader
Organizations
- Indiana University
- Office of Naval Research