An incapacity of normally producing cortisol is a well established medical condition, with known protocols of how to address it taught in all medical schools of the world.
Science has shown that cortisol decreases during sexual arousal, reaching even lower levels after orgasm.
https://pubmed.ncbi.nlm.nih.gov/18624961/#:~:text=This%20has%20been%20demonstrated%20experimentally,decreasing%20cortisol%20during%20sexual%20arousal.
Given that someone has already some cortisol producing issues and decides to have sex in the evening, when we all have naturally lower cortisol, this person can reach an abnormally lower level of cortisol, which is very dangerous.
Actually, it's interesting that in Addison's disease forums, which is a disease of chronically low cortisol, they talk about POIS without knowing what POIS is. They even do their 'pre-packs' before sex, which mainly consists of taking extra doses of the pills they already take to increase cortisol, otherwise they can even 'pass out'.
https://freeimage.host/i/HroRdoghttps://freeimage.host/i/HroRoNtInteresting, isn't it?
There's a concept in cardiology called myocardial stunning.
According to wikipedia:
"Myocardial stunning or transient post-ischemic myocardial dysfunction is a state of mechanical cardiac dysfunction that can occur in a portion of myocardium without necrosis after a brief interruption in perfusion, despite the timely restoration of normal coronary blood flow. In this situation, even after ischemia has been relieved (by for instance angioplasty or coronary artery bypass surgery) and myocardial blood flow (MBF) returns to normal, myocardial function is still depressed for a variable period of time, usually DAYS TO WEEKS. This reversible reduction of function of heart contraction after reperfusion is not accounted for by tissue damage or reduced blood flow, but rather, its thought to represent a perfusion-contraction "mismatch"."
https://en.wikipedia.org/wiki/Myocardial_stunningLikewise, a orgasm for people with Addison's can have a similar effect of making their adrenal glands overloaded, or 'stunned', thus, they will have even lower levels of cortisol afterwards than they tend to have. This 'mismatch' between the amount of cortisol the person needs and the amount it has can result in something called an adrenal crisis:
https://www.uclahealth.org/medical-services/surgery/endocrine-surgery/patient-resources/patient-education/endocrine-surgery-encyclopedia/acute-adrenal-crisis#:~:text=Acute%20adrenal%20crisis%20is%20a%20medical%20emergency%20caused%20by%20a,or%20even%20loss%20of%20consciousness.
I don't believe that people here have Addison's nor adrenal crisis after orgasm, those are extreme cases that can cause death, POISers don't tend to collapse, or die, after orgasm (although they certainly can too in some extreme cases), but if we use the people with Addison's as canaries in a coal mine, maybe we can see things a little bit clearer.