From Mary Shomon,
Your Guide to Thyroid Disease.
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by Mary J. Shomon

September, 2001 -- Researchers at the University of Birmingham in England have finally established what patients have known and many doctors have long denied -- being hypothyroid causes weight gain.

In a study reported in the journal Clinical Endocrinology, the researchers studied 162 people with hyperthyroidism for six months. Those who already were overweight, whose hyperthyroidism was caused by Graves Disease, or who had lost weight prior to diagnosis all had similar amounts of weight gain, which was approximately 5 to 5.5 kg (11 to 12 pounds) over the six months during which they were treated with antithyroid drugs for radioactive iodine.

Those who had their thyroid removed gained even more weight, an average of 10 kg (11 pounds).

And those who became hypothyroid after treatment gained, on average, about 3 kg (6 1/2 pounds) more than those who were either transiently hypothyroid, or who never became hypothyroid at all post-treatment.

Overall, among the entire group, at the end up one year, weight was up by 3.95 (kg 8 3/4 pounds), to 9.91 kg (22 pounds) after 4 years, with a mean weight gain of approximately 3.66 kg (8 pounds) per year.

The researchers concluded that there was substantial weight gain after treatment for hyperthyroidism, and those who became hypothyroid, despite levothyroxine treatment, gained the most weight.

REFERENCE: Dale, J., Daykin, J., Holder, R., Sheppard, M. C. & Franklyn, J. A. "Weight gain following treatment of hyperthyroidism," Clinical Endocrinology , 55 (2), 233-239.

For more information on weight gain and thyroid disease, see the Thyroid Diet & Weight Loss Guide.