I am not sure how many of you who have headache problems have heard of pheochromocytoma, it is a tumor of the adrenal gland. This can cause the following symptoms:
Excess sweating (generalized)
Racing heart (tachycardia and palpitations)
Anxiety / nervousness (feelings of impending death)
Nervous shaking (tremors)
Pain in the lower chest or upper abdomen
Nausea (with or without nausea)
It is rare and typically is not even found until an autopsy after death. If you believe you may have a pheochromocytoma than I would strongly recommend a 24 hour urine test to test for catacholamines. This test measures different types of adrenaline to see if they are out of normal levels. I personally had this test done but all of my catacholamines were within normal ranges.
You could also get an MRI scan done to look at your kidneys.
To find out more information I suggest the following site. http://www.endocrineweb.com/pheo.html