I am taking 300 mg. of lithium carbonate and EffexorXR 150 mg. once a day. I have gained 15 lbs. on the lithium and am very unhappy with that. I have also developed a thyroid nodule (after 2 years on lithium) and am taking 100 mcg of synthroid a day. Did the lithium cause the thyroid problem and is it reversible if the lithium is stopped?