I have taken it for about 15 years.......only 50 mg. It is important to have the right dosage. I had a parathyroid removal this year but I don't think that is related. The dose can be adjusted up and down according to your bloodwork and how you feel.
Synthroid does have a small effect on bone density, but small. I like to go with "brand" drugs since the generics are mostly made in India and don't have the right patent formula and synthroid has been around for a long time.
I use the web site NIH and the Mayo clinic for data - so many unbased comments out there. The company that makes it does have a customer support phone or e=mail line.
Probably not much but I have no side effects...............marceen in the us