I had essentially the same thing. Now DISCLAIMER: Im not trying to scare you.
I had a "benign" 2.45cm goiter on my right lobe, for 2 years they told me I was fine and nothing was wrong, yet I was constantly losing weight and showing signs of being hyperthyroid.
I finally got a good Endo, and told him all that was happening and he said that when he has patients with a goiter close to 3cm, he recommends surgery. They did the surgery about a month ago...........one week later they found out my growth was cancer, one week later had a 2nd surgery to remove the rest of my Thyroid and just this past Friday I had my Radiation treatment.
Im not saying your's is Cancer, its actually a low percentage of Thyroid patients that have cancer, but sometimes blood test dont always tell whats going on with your body and sometimes there are Endo's out there that are either stubborn or just feel like you dont know what you are talking about.
I'd say get another opinion.
If you do get it removed. your probably going to be dependant on synthroid or thyroid hormone replacement for the rest of your life. Would you happen to have thyroid issues in your faimly? if you do, ask them what there symtoms are like or if having children might have caused the goiter. Some woman develope hypothyroidism afer having children... but Good Luck with everything and Try to stay positive because Stressing over health will just not help anything, although you may not help it because the thyroid gland has a lot to do with the nervous system... :)
You doctor should get the ultrasound testing as most informative imaging method.
CT scan can miss many info, there is no excuse for skipping the ultrasound.
The worse mistake is to jump into the quick conclusion.
Wthout the ultrasound the biopsy needle can:
obtain specimen from the wrong area such a blood vessel
hit the nerve or some other areas unrelated to thyroid.
Large cysts on thyroid can be aspirated to relieve compression symptoms.
I never had the same issues as you, but nothing I have read indicates normal blood labs being a cause for a Dx of cancer.
Is there any possiblity of iodine deficiency happening for you?