Doctors don't fully understand what causes POTS in every patient. There are several known causes of POTS, but many patients have POTS with no known cause, called idiopathic POTS.
I have been able to identify, through seemingly endless doctor appointments and tests, the cause of my POTS. I have POTS because my autonomic nerves were severely damaged by an autoimmune disease I have, called Sjogren's Syndrome. The following sections explain the underlying mechanisms of how Sjogren's and autonomic neruoapthy causes POTS symptoms. For the record, I am not a doctor, this is not medical advice, and what I say here may not explain what is causing your POTS symptoms. Here goes...
Low Aldosterone/Low Blood Volume
Through specialized endocrine blood tests we discovered that I have very low levels of aldosterone, an essential life sustaining hormone produced by your adrenal glands that controls the balance between sodium and potassium in your body, which allows your body to absorb and excrete the proper amount of water each day. The adrenal glands are about the size of a walnut and the are located just above your kidneys.
Without aldosterone, you can go into an "adrenal crisis." Your body will become so dehydrated, you can go into shock or, in extreme cases, you could die. Many people with POTS have low aldosterone. There are lots of different things that can cause low aldosterone (high sodium diets, autoimmune diseases atacking the adrenal glands, infections, etc.), but researchers believe that the low aldosterone in POTS is due to loss or damage to sympathetic nerve fibers in the kidney. The kidney detects low blood volume and low blood pressure, and then sends off messages to your adrenal glands telling them to produce more aldosterone to increase blood volume and blood pressure. if any part of this messanging system is damage, including the nerve fibers, your adrenal glands will not get the message and they won't produce aldosterone. In most POTs patients, the adrenal glands themselves are not damaged. They can still produce aldosterone, but they aren't getting the message from the kidneys to do that because the messanging nerves are damaged.
Low aldosterone causes your body to excrete too much water and sodium in your urine, and causes you to have high levels of potassium in your blood. Without enough aldosterone, your body cannot retain the water and sodium from the foods and beverages you consume, which leads to dehydration. Without enough water in your body, you can develop low blood volume. Many of my troubling symptoms of POTS are the result of low blood volume, which doctors call hypovolemia. Studies have shown that many POTS patients are missing ONE THIRD of the normal blood volume expected for someone of their size.
If you were in a car accident and you're leg got cut off and you lost one third of your blood, you'd be in hypovolemic shock and you might die. The ambulance would rush you to the ER and you'd probably get blood transfusions in the ER, until they replaced enough of the blood you lost. Amazingly, POTS patients can live for years with one third of their blood missing, although they sure don't feel good when they have low blood volume.
Low Blood Pressure Triggered By Low Blood Volume
Low blood volume often causes low blood pressure. Since there is not enough blood in your body to push against the walls of your blood vessels, veins and arteries, your overall blood pressure is lower than it should be. 120/80 is usually considered the "ideal" blood pressure for adults, but many people have healthy blood pressure that is slightly lower than this. When I was at my worst with POTS, before any medication to replace my missing aldosterone, my laying down (supine) blood pressure was as low as 80/30 and I could not stand up without passing out, because standing up would have lowered my blood pressure even lower than that.
When a healthy person stands or sits up, the blood vessels in the lower parts of their body are sent messages from various parts of their nervous system telling the blood vessels to constrict, which pushes the blood upwards and counters the effect of gravity. This ensures that blood will reach your upper body and brain even when you're standing up. When someone with low blood volume stands up, even if the messages are sent to the blood vessels in their lower legs, and even if the vessels constrict, there may not be enough blood in their body to supply sufficient amounts of blood to their upper body and brain when they stand or sit up.
The low blood pressure and low blood volume contribute to a lack of blood flow to the upper body and brain - this can cause many of the symptoms of POTS. Sometimes doctors use the term cerebral hypoperfusion, which means not enough blood is getting to the brain. For me, cerebral hypoperfusion seems to cause my headaches/stabbing/shooting head pains, difficulty concentrating/forgetfulness, brain fog, cognitive impairment and not being able to recall the word I am trying to say. All of these symptoms get worse when I sit or stand up.
Tachycardia (Racing Heart Beat)
The blood flow in the human body is run by a very complex system of checks and balances, and I do not claim to understand it fully, but I do know that when receptors in your neck veins, called baroreceptors, notice a change in pressure when you stand up and they send out messages to you heart to beat a little faster and a little harder to ensure that you're brain is getting sufficient blood supply. But in someone with low blood volume, you heart will be faster, but there still won't be enough blood to get to your brain when you stand up, so you're baroreceptors tell your heart to be faster and faster, and you're heart will do that in an effort to make sure you're brain is protected from damage due to low oxygen levels. This results in tachycardia in POTS patients with low blood volume..
My heartbeat will be a pretty normal 60-80 bpm (beats per minute) when I'm laying down, and by simply standing up, totally relaxed, within seconds my heartbeat starts racing up and up to over 130 bpm. The highest recorded measurement I had just standing still for a few moments was 230 beats per minute, which is very dangerous, especially if it goes on for too long. I collapsed to the floor shortly after this reading was taken, probably because my brain was trying to protect itself by making me pass out, which helps return proper blood flow to the brain.
Passing Out/Almost Passing Out
When your heart beating faster and harder isn't enough to compensate for the lack of blood flow to your brain, thankfully, you're brain is smart enough to protect itself from a lack of oxygen, so it makes you pass out, which usually results in you laying flat on the floor. When you lay down on the floor (from passing out or just because you want to), it's easy for your blood to flow throughout your body, and your brain, since your blood vessels don't have to fight against gravity. In that sense, passing out is almost a good thing - it's better to pass out for a few minutes than to suffer with a lifetime of brain injury that was caused by a lack of oxygen to your brain. That's why it's so important for people with POTS to let friends and family around them know that if they feel very lightheaded or like they are about to pass out, the best thing to do is lay down with your feet slightly elevated. Sometimes people try to help someone who is dizzy by holding them up or preventing them from falling out of a chair. While it is certainly polite of them to help, it would be better to safely lay the person's head on the ground and slightly elevate their feet and legs. Hitting your head on furniture or a hard floor is probably the most dangerous part of passing out with POTS, so try to pass out gracefully if you can. :)
I'm "lucky" to get "pre-syncope" symptoms, which means that my body gives me warning signs a few seconds before I pass out (syncope means fainting/passing out). I get lightheaded, dizzy, an off balance feeling, my vision gets grayed out or blurry or tunnel vision, I feel like my blood is being flushed downwards to my feet, my legs feel heavy, like I'm wearing cement shoes, and I usually get a bit sweaty on my upper body, my face turns bright red, I feel shaky and I feel short of breath. Just a few seconds of feeling like that is enough for me to know I have to lay down ASAP, to avoid passing out and hitting my head - which I did a few times when I first got sick, because I didn't realize those were warning signs of an impending fainting spell. Unfortunately, some people with POTS and other syncope disorders do not get any warning signals, and they can be in the middle of doing something and all of a sudden they fall over like a marble statute. If you see this happen, don't lift their head up. Wait a few seconds to see if they "wake up" or call 911 - especially if they hit their head hard or they don't wake up quickly.
In addition to your baroreceptors, there are several other mechanisms involved in the regulation of blood flow. If your brain detects a low oxygen condition, one of the chemical messengers your brain uses to tell you're heart to beat faster, to deliver more oxygen rich blood to the brain, is adrenaline (also called epinephrine). Adrenaline is very good at doing its job and when it is released into your bloodstream, you're heart will be much faster and harder, which is you're bodies way of trying to get more blood to your brain, to protect your brain from injury due to low oxygen. Adrenaline is the chemical that causes that rush you feel when you get really scared by something - it causes an instinctive "fight or flight" response. Lots of adrenaline flowing through you body can make you feel shaky, anxious, jumpy and very uncomfortable. Doctors sometimes use the word tremulousness to refer to this shaky feeling. Too much adrenaline can also cause you to get the chills or to get overheated very easily. Adrenaline can also make your senses feel like they are on overdrive and can cause over-stimulation. Loud noises bother me, and my sense of smell is about 100 times stronger than everyone elses'. This is because your sense are prepped by the adrenaline for a "fight or flight" situation. Just picture a caveman who is all of a sudden attacked by a lion in the middle of the night. His adrenaline would make his body ready to "fight" that lion or take "flight" and run away from the lion. "Fight or flight" is a human instinct that we only need in emergencies, but in some POTSies it's always turned on because of the high adrenaline levels circulating in our blood, as a result of chronic low blood volume and cerebral hypoperfusion.
When I lay or sit still, I can almost always feeling my pulse in my neck, eyes, head, stomach and pretty much everywhere else. When my heart is pounding very fast, I can also see my pulse flashing in my eyes. These are annoying symptoms, probably caused by a mix of the tachycardia, over stimulation and oversensitivity of my nervous system, and the adrenaline surges people with POTS get.
While most people with POTS experience these adrenaline induced symptoms that can look or feel like an almost permanent panic attack, not everyone with POTS has 'true' anxiety or panic disorder. Studies have shown that about 97% patients with POTS were first misdiagnosed as having anxiety or panic disorder, when in fact they really had a dysregulation of their autonomic nervous system. That's not to say that people with POTS can't have 'true' anxiety or panic disorder. After all, half a million people in the U.S. have been diagnosed with POTS. Certainly out of a population that large, there are going to be a percentage of people that have 'true' anxiety or panic disorder in addition to their POTS diagnosis. I was misdiagnosed with about 30 different conditions before we found out I had POTS, with a few ignorant doctors telling me it was "all in my head" and I should just calm down and take a Xanax. I tried Xanax for a day and while it made me feel like a giggling teenager, it didn't do anything to get rid of my POTS symptoms. Ironically, the first doctor who assured me that it was definitely not in my head and that I had a 'real' medical condition and definitely not anxiety or panic disorder was a psychiatrist! He told me the only prescription I needed was a new medical doctor willing to help me figure all of this out. He also told me that people who have anxiety or panic attacks almost always have high blood pressure during the attacks. His big clue that my symptoms were not being caused by a panic or anxiety attack was the fact that my blood pressure would drop to the floor during an attack.
Chest Pains/Tingling Extremities/Tinnitus/Visual Disturbances
The low blood flow to the upper part of your body doesn't just effect your brain and heart. Low blood flow to my arms causes a cold, tingling and pins and needles feeling my your hands and arms. Low blood flow to my chest, lungs and heart can cause shortness of breath (called dyspnea) and chest pains. Low blood flow to my head can cause ringing in my ears (called tinnitus), visual disturbances, dizziness and vertigo.
POTS is not just about low blood flow. Many people with POTS have it because of damage to their autonomic nervous system. Your autonomic nervous system controls your breathing, your heart beat, your blood vessels, your blood pressure, digestion, urination, etc. Basically, it controls all of those things your body does for you that your don't have to think about. For example, when you eat a cheeseburger, you don't have to tell your stomach to digest that cheeseburger for you. Your autonomic nervous system controls the various parts of your digestive tract and takes care of that cheeseburger while you get to do something more interesting.
Dysautonomia can involve damage to the autonomic nerves themselves, or a problem with the chemicals that send messages between the nerves, called neurotransmitters.
Peripheral Small Fiber Neuropathy
My low blood pressure is also partially caused by the fact that the autonomic nerves that control the constriction of the blood vessels in the lower parts of my body are damaged. The damage to these nerves is part of my dysautonomia. I had a small skin biopsy, when my doctors were looking for mastocytosis, another disease that can cause POTS like symptoms. The lab results showed that I did not have mastocytosis, but that my small fiber autonomic nerves at the location of my biopsy (my left calf) were 80% deficient - 60% of the fibers that should have been there were completely missing (as a result of nerve death) and 20% of the fibers were still present, but showed signs of damage. That leaves 20% of nerve fibers that were "normal." Doctors have various terms for my dead and damaged nerve problem - Peripheral Neuopathy, Small Fiber Neuropathy, Autonomic Neuropathy, or Peripheral Autonomic Neuropathy. Neuropathy is a term doctors use to describe when nerves have been damaged or have died off. The name is less important that to understand which nerves are involved, and which of my body systems will be effected by this nerve death/damage.
Roughly speaking, there are two areas of your nervous system: the central nervous system (CNS) which includes your brain, brain stem and your spinal cord, and the peripheral nervous system, which controls the nerves that flow from your spinal cord to the other parts of your body.
Then there are three important types of nerves that can be involved in "peripheral" neuropathy:
-Sensory nerves (that control pain, touch, pressure, hot/cold sensations);
-Motor nerves (that control your ability to relax/contract your muscles, movement, walking, etc.);
-Autonomic nerves (that control your involuntary body functions such as breathing, digestion, blood pressure, heart beat, etc.). In your legs, if you lose autonomic nerves, it impairs the constriction of your blood vessels, and makes it more likely that blood will pool in your legs when you sit or stand upright, causing low blood pressure and all of the symptoms resulting from low blood pressure.
All three types of peripheral neuropathy (autonomic, motor and sensory) generally (but not always) start at the farthest points of the nervous system from the brain. For example, people who have sensory peripheral neuropathy tend to notice numbness, tingling or pain in their toes first, and then if their peripheral neuropathy continues to spread, it can start to move higher up their leg to their ankles, then their knees.
Acid Reflux/Vomiting/Diarrhea/Stomach Pains
When something is wrong with your autonomic nervous system, it's as if there is a short circuit in one or more places in your body and things that were supposed to happen on their own do not work as they should. I developed acid reflux for the first time in my life when I developed POTS. This is likely because the peripheral nerves that control my lower esophageal sphincter - the valve at the bottom of your esophagus that keeps stomach acid down in your stomach - isn't working properly. Sometimes my valve stays open, probably because the nerves that once told it to stay shut are damaged. This valve is probably also "leaky" because my diaphragm muscle, the muscle under your lungs that control your breathing, is also weakened - my doctors suspect this is due to motor nerve damage impacting the diaphragm strength and position. We do know, as a result of pulmonary function tests that my diaphragm strength is about 70% weaker than it should be.
There are also nerves that control how quickly something passes from your stomach to your intestines, and how quickly something travels through your intestines to... well you know.. the toilet. OK... if you don't want to hear about this, skip to the next paragraph. While I don't want to gross out anyone reading this, especially those of you who know me, I think it's important to share this information with other POTS patients so they know they are not alone in suffering, and so that maybe someone else suffering with these symptoms will go to their doctor with this info and get an accurate diagnosis. So grow up... everyone poops! I had horrible diarrhea when I first came down with POTS - several times a day for several months, usually starting when I woke up in the morning and lasting until about 3 pm. At the same time this was happening, I was puking several times a day for about the first three months. Of course that caused me to lose about 50 pounds within the first few months I was sick. I became malnourished and dehydrated an my hair was falling out, even though I was eating a very healthy, but high calorie diet, and I was drinking 2 liters of water and electrolyte fluids (PediaLyte and Coconut Water) a day.
Thankfully my bowels are doing a little better now, but my stomach symptoms still act up every day, and we're not really sure what triggers it, but we have some educated guesses. I'm back to a healthier looking 133 lbs. and I really have to work at it to keep my weight up (mostly I'm worried that losing weight means I'm not absorbing the vitamins and minerals I need to get healthy). I get acid reflux several times a day, with the acid going all the way up into my throat and then into my lungs, which triggers really bad breathing problems (and my asthma inhaler does not help when I get short of breath from the acid reflux). My doctor thinks I have something called gastroparesis - when your stomach does not empty the food you ate into your intestines. I get a bloated/full feeling even from eating small meals, I get stomach aches if I drink too much water at once, I vomit about once a week on average - usually right after drinking fluids - we're not certain, but it is probably because the autonomic nerves that control the speed of my digestion or my stomach valves are damaged. This are unpleasant symptoms that sometimes consume many hours of my life, but it could have been worse. Some people with autonomic nerve damage cannot control their bladder or their bowels at all, or their digestive nerves and muscles are so damaged, they have to get their nutrition thru a feeding tube. I consider myself lucky that those parts are still working for me.
Your autonomic nervous system also plays a big role in regulating your body's temperature. It's likely that the chills, goosebumps, overheating and night sweats I get are because of damage to some of the nerves in my autonomic nervous system, although these body temperature related problems can be exacerbated by too much adrenaline as well, which is discussed above.
Shortness of Breath/Hyperventilation/Sore Neck and Shoulders
Many people with POTS, myself included, have persistent shortness of breath. In my case, it seems to be worse when my other symptoms are worse, it's worse in the morning, in the cold and it also seems to be worse when I stand or sit up. Many POTS related problems can contribute to shortness of breath, and in my case I honestly don't know what's causing it, but my doctors suspect, in part, it has to do with the low blood flow to the upper part of my body. If my heart or lungs aren't getting enough blood, I end up gasping for air, feeling oxygen starved. It could also be caused by damage that may have occurred to my peripheral autonomic nerves in my controlling my heart/lungs/diaphragm.
When I feel short of breath, sometimes I start to hyperventilate. Many people associate hyperventilation with anxiety, and just think "if you calm down, you won't hyperventilate." In some cases, I'm sure that's true, but my hyperventilation only happens when my other symptoms are bad or when I've been standing upright too long and my pulse starts to race, so my doctors have reassured me that it is more of a biological trigger than an emotional one. Let me be clear - it is pretty terrifying when you feel like you can't breathe and your heart starts racing to 130+. Even the calmest person in the world would get a little rattled if that was happening to them several times a day without explanation! I'm sure the surges of adrenaline (explained above) and the racing/pounding heart beat don't help the breathing situation either.
Hyperventilation can also be a sign of an acid-base imbalance. When you hyperventilate, you blow out too much carbon dioxide, which your body needs to maintain the pH balance of your blood. When you hyperventilate, your blood may be fully oxygenated, but the abnormal pH of your blood makes it difficult for that oxygen to reach the tissues that need it - essentially causing a low oxygen condition even though your blood is filled with oxygen. Many different medical conditions and medications can cause a problem with the pH balance in your body, including low aldosterone and some drugs used to treat low aldosterone. My doctors have just ordered some more tests to see an acid-base disorder this may be contributing to my hyperventilation and shortness of breath.
All of this gasping for breath usually results in me breathing shallow breaths from my upper chest area, rather than using my diaphragm to breathe deeply. This may be the way I breathe because my diaphragm is damaged, as explained above, but it's also natural to breathe quick shallow breaths when you hyperventilate or have other breathing difficulties. Repeated shallow upper chest breathing can put a strain on chest, neck and shoulder muscles, and that is probably why they get so sore sometimes. Also, since people with POTS tend to lay down so much to avoid passing out, they may be developing bad posture or may be weak from inactivity. I am definitely guilty of this. When I was in the hospital for two months, I could barely hold up the weight of my own head because my neck and back muscles had become so weak. That started because when I was first admitted to the hospital, they wouldn't let me out of bed AT ALL because they didn't know why my heart was racing so high every time I stood up. It was really degrading - they made me use a bedpan to go to the bathroom for a few weeks. I was not happy about that and I didn't think it was necessary. Sometimes if the nurse wasn't around, I sneak over to use the bathroom, holding on to my IV pole for balance - within seconds the nurses would come running in to my room screaming at me because my heart monitor alarm would start beeping because my heart was racing off the charts. Of course, all of that forced bed rest only made all of my symptoms worse. I eventually convinced them to give me one of those little portable potties, so I could retain a tiny fraction of my dignity!
I am extremely tired all the time since I developed POTS - just washing dishes for a few seconds or walking from my bed to the bathroom makes me exhausted. When you heart beats so fast just from sitting or standing up, naturally - you get tired really quickly. It feels like I've just completed a hour long cardio work out, without that energizing feel good sensation you get after a real workout.
Lots of POTSies report feeling very tired after a passing out episode. I tend to get very, very tired and groggy right after a bad "breathing attack." When this happens, it's almost like I can fall asleep as soon as I shut my eyes, even if I'm laying on the kitchen floor or in the middle of the ER. Low blood volume also contributes to fatigue, because you don't have the ideal amount of red blood cells to carry oxygen to the cells in your body. In addition to the fact that I have low blood volume, they also found that I had low hemoglobin levels. Hemoglobin is the part of your blood that carries oxygen to you cells.
It can be hard for me to fall asleep at bedtime. It's pretty difficult to fall asleep with your pulse racing and your head spinning with dizziness and your pulse flashing in your eyes, and thumping in your neck and temples, and don't forget the stomach aches and acid reflux creeping up into your throat. I have to fall asleep with the TV on and the volume turned up pretty loud. That way I can't hear my pulse and I can't see it in my eyes because the ambient light and flashing from the TV masks it. I frequently wake up in the middle of the night with terrible night sweats and a shaky feeling. All of this contributes to fatigue as well.
My doctors also found that I have low Vitamin D, which is common in POTSies. At time throughout my illness, I have had low calcium, low magnesium, and low potassium - even though I am eating a very healthy diet and plenty of food. My body may have trouble absorbing all of the nutrients I eat because of the gastrointestinal problems I'm having. All of these vitamin & mineral imbalances can contribute to fatigue.
Many of the symptoms listed above can be caused by, or made worse by, something called reactive hypoglycemia. Some POTS patients, especially those with severe gastrointestinal symptoms, have reactive hypoglycemia.
Hypoglycemia is a fancy term for low blood sugar. You may have heard of hypoglycemia if you know someone is diabetic - however reactive hypoglycemia is not the same thing as diabetes.
Reactive hypoglycemia is a sudden onset of low blood sugar about 1-2 hours after eating a high carbohydrate meal. Because it happens after eating, it is sometimes called post-prandial hypoglycemia ("post" means after and "prandial" means eating). The symptoms of reactive hypoglycemia are essential the same as the symptoms of hypoglycemia caused by diabetes (and these symptoms overlap with many POTS symptoms), such as:
-flushing (skin turning bright red)
-getting the chills/feeling cold
-tingling/coldness/numbness in hands/feet
Not all hypoglycemic episodes involve every symptom. Severe episodes of hypoglycemia can result in coma or death, and repeated episodes of hypoglycemia can lead to complications over time, so this is not something you should ignore if you think you have it. An endocrinologist would be the type of specialist best adept at diagnosing and treating this.
Reactive hypoglycemia has several known causes, and it is more common in thin people and those who have had a recent dramatic weight loss or illness - categories that many POTSies fit into. There is also something called Adrenergic Postprandial Syndrome, which mimics reactive hypoglycemia, in that the symptoms occur 1-2 hours after eating, but it differs because no decrease in blood sugar can be found in blood tests during an episode of symptoms. Doctors who have studied this believe it is caused by dysregulation of the autonomic nervous system leading to an increase in production of adrenaline (which of course, means it is a form of dysautonomia, just like POTS).
The treatment is usually similar for all cases of reactive hypoglycemia:
-Eat protein with every meal (eggs, meat, fish, dairy, soy, beans, nuts, legumes).
-Choose complex carbohydrates (veggies, whole grains, dairy) over simple carbs (sugar, honey, white bread).
-Eat high fiber foods, and consider supplementing your meals with soluble fiber.
-Eat food with a low to moderate glycemic index (you can look this up on the internet).
-Eat small meals and snacks about every 3 hours, rather than 3 big meals a day.
-Do not be afraid of healthy fats (nuts, olive oil, fish oil) since fat reduces insulin demand.
-Avoid sugar in all forms, especially in an empty stomach.
-Avoid white refined foods (those with refined flours-cakes, cookies, pretzels, regular pasta).
-Avoid alcohol, which is high in carbs and low in nutritional value.
-Exercise regularly (hard for POTSies, but just try your best to move a little every day)
In severe cases that cannot be managed by lifestyle and dietary modification, there are some drugs available.
So those are the basics of what causes some of the more common POTS symptoms. If you want to learn more about the causes and effects of autonomic dysfunction, there are many journal articles on the subject and a few non-profts out there working to educate people on this topic.