In my opinion your Dr. is doing a good thing for you by addressing your thyroid problem.
Low Thyroid and low body temps seem to be very common with Lyme, and according to our Dr., alot of symptoms go away once it is fixed. That is good news as I see it.
Don't assume all things ending with -oid are steroids or are are evil. We die without Thy-roid from some source for instance.
The Steroid drugs used to treat inflamation work by suppressing the immune system... the last thing we need while fighting an infection. That is why steroids are evil drugs when you have Lyme Disease.
The low thyroid condition common with Lyme is sometimes called Wilson's Syndrome. There have been some discussions about this over the past few weeks. (Use Search)
My wife and I are in the process of having this checked out on ourselves right now. Some others have had treatment and can share personal insights.
I don't recall that Synthroid is the preferred medication for this, but that varies by individual need.
Your Dr. is on the right track wanting to take care of the problem, though.
Again... Welcome!
Thyroid tests can be tricky. My LLMD put me on Armour Thyroid because I had clinical signs of hypothyroidism...although my tests came back within normal range. I am on a low dose and have tests done every three months which continue to be in normal range.
Many people have good results with the Armour because you get the proper balance
with less need to make adjustments in the dose.
www.armourthyroid.com
Welcome to lymenet and you are lucky to have a doctor willing to address this for you!
Best of luck! nan 
[This message has been edited by nan (edited 16 February 2005).]
[This message has been edited by nan (edited 16 February 2005).]
I'm been on synthroid 20-25 yrs. Found out last summer I have late stage chronic lyme; misdx for 34 years.
It will help you. My dosage lowered last year finally.
Also, Laurie, in the future please use shorter paragraphs of 6-8 lines only. You'll find with our severe brain fog we just can't comprehend things. By breaking it up, we can read and reply better.
Also, look for TREEPATROL'S newbie links. Print it and check off as you read as there are months of reading there.
Glad ot have you aboard. Betty G., Iowa