Hello, Typically, the symptoms of cycles of nausea and vomiting suggest problems directly in the GI tract, HORMONES that may be cyclically abnormal, or a Central Nervous reaction to some metabolic or physical derangement. When I say hormones I m not just talking about THYROID products. In his case, I would be checking BLOOD SUGARS before and after meals and directly measuring for insulin levels which can be way too HIGH and cause these symptoms. There is something called POSTPRANDIAL HYPOTENSION which could be mistaken for some type of cardiogenic dysautonomia as well or at least make it difficult to tell them apart at times. I would also recommend provocative ADRENAL GLAND FUNCTION TESTING and look at catecholamine levels (biochemical products of hormones released from the gland) to see if we are creating some sort of adrenalin storm/rush that can also drive some of his symptoms or NOT ENOUGH which could explain the unusual amount of fatigue. As far as the GI tract is concerned has he had either an UPPER GI SERIES using barium to clear for things such as ulcerative conditions in the stomach or duodenum or even mass lesions (he chews which puts him at risk for cancers)? This doesn t look like IBS (Irritable bowel) but on the off chance that he could react in an allergic fashion to something he s ingesting. Has he changed his brand of chew recently? Eating some sort of different diet? Are these cycles at all tied to the period of time just before or shortly after meals? Has he tried removing things such as GLUTEN, ARTIFICIAL SUGARS, and FOODS/BEVERAGES containing large amounts of caffeine such as MONSTER or RED BULL? As far the nervous system is concerned, you ve already mentioned a diagnosis of cardiogenic dysautonomia. How about something a bit more global to tie in the GI symptoms as well such as an autoimmune process that specifically targets the autonomic nervous system such as Sjogren s disease, lupus, or alcohol abuse? All of these can target and dramatically affect autonomic system function leading to cyclical vomiting spells. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Dariush Saghafi, Neurologist