I originally was on Synthroid, prescribed by my family doctor. Soon after my diagnosis I went with my Mom to her endocrinologist, and asked what he thought about Synthriod. His words "Terrible stuff, we never use it in our office." Told me to try an experiment when we got home. Take 2 glasses of water. Drop a Synthroid in one, and a Levothroid in the other. I did it. The results - the Levothroid started to dissolve as soon as it touched the water, and the Synthroid just dropped like a stone and sat there. I left the Synthroid over night in the glass, and it was still solid in the morning. I had to grind it with a pencil to dissolve it, after 18 hours in a glass of water. I immediately had my prescription changed to Levithroid.
Things went well for about two or three years (I can't quite remember the timeline) and then I started having symptoms of low thyroid again - tired, dry skin, hair falling out. Went to the family doctor, had blood tests, he says my levels are fine, these symptoms can be caused by stress and maybe I need to see a psychiatrist. OK, time to do some research and go see an endocrinologist. My research showed that some people need some T3 along with the T4. Armour Thyroid which has both T3 and T4. That T3 can make some people feel much better. The endocrinologist looks at the blood tests and says my levels are way too low. The recommended levels have been changed and the reference levels shown on the blood test results from most labs have not. So the family doc has been basing my dosage on the reference levels (which were correct when he went to med school). I ask if Armour would work for me and he thinks so. I've been on it for four years now with great results. The only difference is I take the Armour twice a day, instead of once a day with the Levithroid.
So if you don't think you are getting the right care from a family doctor, go see an endocrinologist.