There are a lot of problems with synthetic thyroid treatment and many women have their health messed up. Revealed  in the books "Stop the Thyroid Madness" and "0vercome Thyroid Disorders" by David Brownstein MD. Hypothyroidism often follows menopause, hysterectomy or excess stress. It is important to be producing enough estrogene to balance with thyroid, pituary and others glands  in equal balance.(in my own case) . Also the importance of iodene needed by the Thyroid (found in Kelp tablets) and is said to protect against breast Cancer. Most people are low in iodene . Margaret Randall