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Synthroid® is a prescription medication used to treat hypothyroidism, in which the body under-produces thyroid hormone; some people simply do not produce enough thyroid hormone, while others produce none at all, and Synthroid® is a synthetic thyroid replacement that is prescribed and monitored by a doctor to correct that. The connection between weight gain and Synthroid® is somewhat difficult to pin down, because some people lose weight while taking the medication, while others gain it. Theoretically, weight gain is not a side effect of the drug, but there are numerous patients who state that their weight gain began when they started taking Synthroid®.
When considering Synthroid® and weight gain it is important to consider the results of one's bloodwork and any other lifestyle factors that may be contributing to the weight gain. There are a number of different thyroid hormones in play in the body, and it is important for one's doctor to monitor the levels of all of them, not just the most common, which is TSH. Altered levels of T3, for example, may be contributing to the weight gain even if the Synthroid® is correctly regulating the levels of TSH in the body. It is best to become as informed as possible about hypothyroidism and bring these questions to a physician; if the physician isn't willing to answer them thoroughly, then find another specialist who will.
Usually, the connection between weight gain and Synthroid® goes in the other direction. Hypothyroidism often causes people to gain weight because the metabolism becomes very sluggish. When Synthroid® is taken, the metabolism speeds up again to normal levels, often causing weight loss. Sometimes, individuals will need their prescriptions adjusted if the Synthroid® amount is too high and is causing too much weight loss, which can actually push the body in the direction of hyperthyroidism. Some people find that this makes them especially hungry, however, which can start the cycle all over again.
In reality, there is no simple connection that exists between weight gain and Synthroid®. If someone feels that their weight gain and Synthroid® use are connected, it is necessary to discuss it with the doctor and perhaps explore other methods of treatment, such as natural TSH replacement, or even a supplement of T3. Dietary and lifestyle changes will be necessary as well, since some foods can also slow the thyroid and prevent production of thyroid hormone. In addition, exercise can help to boost metabolism and promote weight loss, even though it will be considerably more difficult with hypothyroidism.