Can anyone tell me what causes changes in thyroid levels? I was diagnosed Hypo over a year ago and after months of dosage changes, finally got stable levels and stayed that way for 6-8 months. Now suddenly, my levels are off again and we're back to the dosage yo-yo game. I started Atkins 2 weeks before the off-level testing. Would this have made any difference? What causes changes in thyroid levels anyway? DUH...I know I should know this...