This is a question we receive commonly when we are evaluating new patients. We have definitely heard this question more frequently in the past few months, likely as a result of Oprah's recent article about her battles with her hypothyroidism. That may be giving Oprah a lot of credit, but many more people seem to be aware of the impact that thyroid function can have on basic their metabolism. We have seen a number of people who are currently being treated for hypothyroidism, and they have a number of concerns as well related to their thyroid function and their body weight.
The thyroid plays a central role in regulating metabolism and several metabolic processes. The thyroid gland is found in the neck and has two lobes on either side of the larynx. The thyroid is controlled by the pituitary gland. Most often, people who need hormone replacement thyroid have either had their thyroid removed or damaged due to radiation therapy for some other type of illness. Replacing the thyroid hormone is a standard medical practice and routinely done by primary care physicians and endocrinologists.
When there is not enough thyroid hormone, the body will work to conserve energy. Reflexes will slow, you generate less heat (i.e. you will be more sensitive to cold temperatures), and you may gain a few pounds. While everyone is admittedly different, it is unlikely that mild levels of hypothyroidism lead to severe, rapid weight gain. Once your thyroid hormone is replaced, these symptoms should resolve and your weight should return to normal. If you are continuing to have difficulty with your weight following adequate replacement, it may be necessary to measure your resting metabolic rate and adjust your energy intake and level of physical activity to be appropriate for your metabolic rate.
Can the thyroid hormone be used to actually promote weight loss? Research has shown that using thyroid hormone as a method for weight loss can have deleterious effects on bone health and heart health. The amount of additional weight loss achieved beyond calorie restriction and increased physical activity is not substantial, especially when considering the side effects. The one area of interest that remains is the use of supplemental thyroid hormone to prevent naturally occurring declines in resting metabolic rate during calorie restriction. The use of supplemental thyroid hormone in this situation may promote consistent weight loss over a longer period of time, preventing plateaus. However, even in this situation, the thyroid hormone levels should not be above the normal range.