“…for example a low thyroid person who can't produce much metabolic energy is very susceptible to drinking too much water and getting a very general disruption of their physiology. A pint or so of water passing suddenly through your stomach to your intestine is a surge of serotonin release and that's simply a model of stress or shock in general. Anything that shocks you or stresses you tends to start the same process but just a surge of water hitting the intestine is enough to increase serotonin”