As long as the synthroid dose keeps the TSH in the desired range (0.5-2.0) there should not be a problem - do not excede the recommended dosage for the Z-3 product and make sure that diet and exercise (the real keys to weight loss) are incorporated in your plan.
I saw your question far below on the questions page. Your situation needs some input for sure. If you can, post again as a new question and Dr. Mark will see it and be able to respond, as well as other patients on here.
You might even try posting a new question now but if it pops up the notice saying the question-quota is already used up for the day, try again in the morning and if that notice pops up again, keep trying a little later in the morning because I believe each new day for questions, opens approx. 10:00AM central time.
Just as an initial reaction to your question, it sounds to me you need more stable dosing. It might benefit you more to be taking a combo T-3/T-4 medication like "Armour". Some Dr.s avoid this brand, due to negative hype by Pharmaceuticle companies in competition to get their brands a bigger share of the market. One claim they make is that Armour has "dosage inconsistency" but this very same claim has been made about Snythroid and there were even recent lawsuites filed for this reason with attempted injuctions filed to keep it off the market. The point being that if a prescription for a med is still available, this means people are still being successfully treated with it. Like many others on here, I admit I have a lot of confidence in Armour natural brand of hormone replacement med. That's not to say Synthroid and the other synthetics don't work for certain people.
How about it other forum members, any input for Ruffian? You'll find his question pretty far down on the questions page.
Thanks,
Jim