There is alot of information on mixing birth control with thyroid medication. Simply, most information I came across says taking birth control meds will deplete your thyroid medication and lower thyroid function.
May alter TSH testing.
You may want to take a look at this old post from an expert side ( Doctor) here on Med Help
http://www.medhelp.org/forums/mentalhealth/messages/30184a.html
I have also read similiar sources of information as the MD states in this post on mixing Prozac with hypothyroid medication. It is an alter of brain receptors/ mood stabilizer and may throw off certain levels of other hormones.
I was also on Xanax to relieve my anxiety during my symptomatic time with hypothyroidism. It seems to do the job until my levels stabilized and the anxiety became less noticeable and eventually dissappeared when I reached an optimal level of thyroid medication.