Norepinephrine, a neuroendocrine hormone boosted by cold exposure, increases mitochondrial biogenesis.

“So maybe there's a good opportunity to, so cold and UCP1, if you could educate us on UCP1. I find this really interesting, and I learned about it from you. - Yeah, well, so norepinephrine actually released in the plasma. It does act as a hormone. Vasoconstriction is one thing it does, but it also regulates a variety of molecular functions that have to do with adaption to cold, one happening to be, shivering is a very inefficient way to produce heat, which is what your body's trying to do when it's exposed to cold, and your muscles are basically contracting and producing heat from that, but that's just not very efficient. So the more eloquent way to do it, or elegant, I guess, way to do it is to basically have your mitochondria produce tons and tons of heat. So the way it does this is by activating a gene called UCP1, uncoupling protein 1. Norepinephrine is upstream of that, activating it.”

“Norepinephrine is upstream of that, activating it. What that does is, essentially, so mitochondria are these little organelles inside of your cells that are responsible for producing energy. Usually, that's in the form of adenosine triphosphate, ATP, and that's what lets everything function inside of your body, from your neurotransmitter production to your heart beating, et cetera. However, you can uncouple your mitochondria.”

“Cold-water immersion produces beneficial brain & metabolic effects that converge on norepinephrine, a neuroendocrine hormone boosted from cold that increases mitochondrial biogenesis.”

“when acting as a hormone norepinephrine causes your blood vessels to constrict which helps you retain heat but retaining heat isn't the only way our bodies maintain their temperature we can also produce heat a process called thermogenesis ... non-shivering thermogenesis is direct metabolic heat production and norepinephrine plays an important role here too it acts on key proteins such as ucp1 in fatty tissue these proteins disconnect the normal electrical processes within our mitochondria that produce chemical energy and instead allow them to directly produce heat”