They are most definitely reversible. I was hypothyroid for 20 years. The medication given me which which was synthroid, never did the job. I always felt some type of fatigue. Well, I met the folks at the Iodine Forum and because of them, I am happy to say that I am no longer hypothyroid and........... I do not rely on any medications. After just a short time of following their instructions and supplementing with Iodine, I was fine. To this day I have energy and feel so much better than I had for 20 years under a doctor's care. Go to the Iodine Forum and get their advice.