I Have Thyroid Nodules And Am On Erfa For My

I have thyroid nodules and am on erfa for my thyroid issues. I have been on 60 mg dosage and as of today it has been reduced to 45 mg. I had blood work done and my T3 and T4 were within range, but my TSH is at 0.10, down from 0.96, nine months ago. I am 55 years old and post menopausal. Is Actalin something that I should be taking? Btw I had an ultra sound on my nodules a year ago and then recently and they have remained the same size. What causes these nodules?