I ve had hypothyroidism for 30 years and it s been well controlled by a low dose of Synthroid. For some reason my thyroid stopped functioning sometime over the last year or so and now I m working with my MD to increase my medication dosage to get my levels back up to normal. What might account for the drastic change? I had a major surgery (spinal fusion) sometime before the change in my thyroid function. Before the surgery I had been feeling hot all the time (since menopause- 10 years) but immediately after the surgery that changed; I now respond to temperature like other people. Is that a clue that the surgery kicked off some metabolic/hormonal changes?