Blood test question

[Rachel4]

I start Levoxyl on Dec 4 and my endo wanted to retest after two months. I got my lab orders and the endo only ordered TSH testing. I originally had TSH, free T4, and free T3. She also tested for antibodies which came back negative.

So why not T4 too since I've been taking synthetic T4?

And why not T3 to make sure the T4 is converting correctly?

I'm going to call about it but wanted to get some more information.

[laura1967]

I agree that you should have had all three tests done again. And, your retest should be done around the 6 week mark. I think I would start questioning this dr...if he isn't going to run the proper tests than find another. He may be an endo who specializes in diabetes like so many others....they only know the very basics of thyroid. Good luck. :)

[gimel]

To the detriment of their patients, too many doctors have the mistaken opinion that TSH is the only test they need to diagnose and treat thyroid problems.  How many times have we heard from members of this forum about how they had to insist that their doctor run the most important tests-- for free T3 and free T4, and even then were not always successful in getting that done?

[Rachel4]

Called and talked to the doctor's nurse. I questioned just doing TSH and not T3 or T4.  They assure me TSH is all the doctor needs. I need help understanding this better!

Here is how I understand it:
1. The hypothalamus sends message to the pituitary gland to create TSH and monitor the thyroid hormones.
2. The pituitary gland sends TSH to the thyroid (instructions to create mostly T4 and a little T3).
3. The T4 needs to convert to T3.
4. Message is sent back to the pituitary gland to report thyroid hormone levels which determine if TSH is created (negative feedback cycle).

So the TSH report is the measurement of whether the pituitary gland thinks more thyroid hormone is needed.

What other information can you provide?

Thanks!