Hi Ryan,
Firstly - I would not want to wait 3 months for the eye to be investigated further! Carcinoids/NETS can show up anywhere in the body, not just the gastro tract - they have even been found in the sinus, and the middle ear.
I, too, am 38, and at the time I became acutely ill in 2009 I was the healthiest and fittest I had been in years. I have carcinoid syndrome and am on Sandostatin, but no tumours (Australian spelling) have been found. Some docs disagreed with the diagnosis because of this, but my Mother got diagnosed last year when they found 9 carcinoids (all smaller than 8mm) in her small intestine when doing surgery for something else.
What sort of PET scan did you have? Normal (glucose-based) PETs are usually not effective in finding carcinoids because they are designed for fast-growing cancers. The only PET I have heard of as being effective is the Gallium 68 Dotatate or Dotatoc scan. Having said that, I have been having this scan every 12 months for the past 3 years and nothing has shown up.
I have had every scan and 'oscopy that you can get and they have been unable to find my tumours. Most of my blood tests have been normal and my 5HIAA has always been normal. The only indicator apart from my symptoms was a sometimes elevated blood serotonin. The reason it is only sometimes elevated is probably the same reason you only sometimes have diarrhoea - these tumours can be "cyclical secreters", so you may only be getting the hits of hormone release sometimes, not constantly.
It's strange because having an elevated normetanephrine and headaches sounds more like a Pheochromocytoma, another type of NET, but it doesn't mention diarrhoea as a symptom.
It might be worthwhile getting a copy of the latest diagnostic manual which you can download free off the internet. I can't remember the web address but the title is: "Neuroendocrine Tumors : A Comprehensive Guide to Diagnosis and Management" and they are up to the 5th Edition.
If you want me to send you any other info I have gathered on Carcinoid, just send me your e-mail address in a private reply.
Blessings, Lauri.