I am inquiring about the effect of the TB drug isoniazid and its effect on thyroid function. My skin test was positive in 2006 and I was treated with the isoniazid+ Vit B 6(?) for duration of 6 month. starting in 2007 I had significant weight gain and developed frozen shoulder. During that time I had various symptoms ranging from irregular menses, constipation and hair loss.... it wasnt until summer of 2009 that I realized I have thyroid issues as I suddenly had a painful episode of acute thyroiditis. Prior to the hyperthyroid episode, I never thought that my symptoms may have been related to thyroid and never had a thyroid test done. I have no family history of thyroid illness. It is one year later and my thyroid levels (TSH and T4) seem to be flucutating. I went from Hyperthyroid to hypothyroid to normal levels. Lately some of my symptoms have returned i.e constipation and hair loss and blood test showed high TSH, T4 still with in normal range. My question is if you know of any interaction between TB drug and thyroid function? and if my thyroid disease is a result of such interaction would this condition pass? thanks