I just looked at your profile and see that you're a fellow Oregonian...I'm in Sisters.
If you check the Synthroid website, I believe you will find that if you are over 50 or have been hypo for more than a few months or have a heart arrhythmia, the recommended starting dose is 12.5-25 mcg. Meds can be slowly increased if they are well tolerated. It's better to start out at a low dose and increase slowly than to start out too high and have to backtrack.