When my thyroid levels are off I experience joint pain. Actually, feeling arthritic is often a hypothyroid symptom.
Since you just started taking Synthroid, I'm wondering if you are going thru an adjustment period?
Normally, retesting is done within 2 months of beginning a dose, or increasing a dose. So, perhaps you will soon be retested?
It took awhile for me to "stabilize" on an optimum dose.
Actually, taking estrogen can affect our thyroid status. They use the same cell receptors -- and estrogen can reduce the amount of thyroid hormone available to you -- which could have made you somewhat hypo, creating joint pain. Understand, this is a guess.
By the way -- did your doctor share the treatment objectives? Where your TSH should be? What your T-3 and T-4 hormone numbers should be? So many doctors treat to different levels, it is good to learn about these numbers and what they mean. Be sure you get copies of your test results and keep them, jotting down how you feel at the time.
Figure that you will be able to work this out-- but that it may take a few dose adjustments. ~ Maureen
There are several relations between the hormones, I have not seen joint pain as a problem however. If the levels were low then the synthroid is appropriate and ultimately may help the shoulder pain -- there may be a relationship with hormones in your case, this is not typical, but with thyroid and other hormones one never can say never.....consider a rheumatology evaluation if the pain continues.
We do know that hypo/hyper thyroid left untreated can cause joint pains....