I m a 33 year old Male, and for the last 18 months, I ve had the following symptoms: Primary issues - periods of elevated heart rate - High Serotonin levels - Frequent urination RANDOMLY SPIKING HEART RATES resting pulse is normally high 60s. At least once every day, that rate jumps to somewhere in the 90s for a few hours - this appears to coincide with food intake, but can t be directly attributed to any particular kind of foods. And it doesn t always coincide with meals of any size I ve experienced a decent degree of orthostatic intolerance - First thing in the morning when i get out of bed my heart rate goes from 60 - 120+ , this can persist during the daytime, with a standing heart rate around 15-30bpm higher than sitting. But it doesn t happen all the time. Sometimes my standing heart rate is just fine and sits 1-5bpm over sitting. CRIPPLING EMOTIONAL TROUBLE Over the months I ve become insanely neurotic about what could be causing it. I m depsressed and anxious most of the time. I get paranoid about certain foods such as those high in Amines, or Serotonin (more on that later), I avoid eating too much salt.. so I end up losing a lot of weight due to not eating much.. When this first started, I lost 15kgs in the space of 2 months, and I wasn t fat to begin with. In fact when this all began, I was exercising 5 days a week (no enhancing drugs). I m debilitated by anxiety around medications. I ve tried SSRI s which made me scarily sleepy and pushed up my heart rate (you ll see later this is unsurprising as my serotonin levels are extremely high). When I take drugs like Xanax my anxiety drops a bit but my heart rate goes HIGH even when im sleeping.. so on xanax, my sleeping heart rate is ~100 rather than 50-55 normally. Propranolol is the only drug I ve taken that seems to help, but that is more a band-aid solution. I get terribly depressed very easily. I have anxiety around my pulse most of the day every day. I was exercising every day for 1 hour (mild walking exercise), and meditating 30 minutes every day, but neither had any appreciable impact. It should be noted that before this all started, I had a history of panic attacks which were mostly well controlled by meditation/exercise/lifestyle. FREQUENT URINATION Now, this isn t the kind of frequent urination of a weak or small bladder. This is the kind of urination where my body just doesn t hold onto water. I can drink a glass of water, and 15 minutes later, urinate a huge amount out, almost completely clear. My urine can be clear even if I m just drinking 750ml of water a day. I don t feel thirsty ever, and have water around me all the time if I want it. I don t drink coffee, tea, or any other kind of diuretic. This non-ability to hold onto liquids comes in phases, and generally (but not always) seems to coincide with my episodes of worse heart rate troubles. WHAT HAVE I BEEN TESTED FOR Not surprisingly, I ve had a lot of tests. 1) Pheochromocytoma tested twice - negative 2) I ve had 4 sets of 24 hour rate monitors, nothing interesting found 3) My thyroid profile is fine 4) My diatbetes test came back negative 5) My red/white blood cells are fine, but i do overproduce red blood cells but only just above normal limit. 6) I ve had a heart echo all fine 7) An endochrinologist then saw me and suggested i get tested for carcinoid - So I had my urine 5HIAA tested which was negative, but my serum serotonin was 2220 H nmol/L when the upper limit for normal is 1200. He then re-tested my serotonin suspecting a possible error, but this time it came back as 3730 H nmol/L which is over triple the upper limite. (yes I was on the correct diet beforehand) He then tested my chromogranin A, which came back normal. He then ordered an abdominal scan and a Dotatate PET scan and neither showed up anything. Cool My blood pressure is generally high. It s never low, and never extremely high. It sits around 130-140/80-95 9) My electrolytes were tested upon 2 hospital admissions and were fine both times I have no idea what to do from here. I live around the world with my partner working online, my specialist is in Sydney, Australia. I can go back to him, but another appointment will be months away. I m currently in Chiang Mai Thailand, and went to an Endochrinologist here who was clueless about serotonin issues and was using google to try to help. Obviously not the expert I need. The last week or two have gotten much worse... my heart rate during the day stays around 80bpm sitting, and 100bpm standing (I know that s not crazy high, but it s higher than my normal levels which would be 65 sitting and 70 standing). I feel tired a lot of the time, and I occasionally get hot flashes where i feel hot even in an air con room, and start sweating. I tried a small dose of propranolol yesterday, but it didn t seem to work at all, and it appeared to make my sweats and hot flashes worse. I have some questions I wish I could find answers to. They are. 1) Is it possible to be serotonin resistant? I have high serotonin levels, but my symptoms best match up with low serotonin problems. And cutting out serotonin foods or generally eating less seems to make things worse not better. I can t find anything much at all on it. 2) How can i have high blood serotonin, but not be secreting out much 5HIAA? If it s not a carcinoid, what could cause that? 3) What else should I get tested? If my serotonin levels weren t so high I d have to assume this was some extreme form of anxiety. But most of my research suggets chronic stress should lower my serotonin levels, not increase them. I m not necessarily feeling any stress when i get my heart rate spikes, they can be triggered by stress, but often they come when im relaxed doing something calm.