Hi,
Many of us with Graves' disease have taken diet pills or been on special diets or exercised compulsively before we were diagnosed. Older studies showed that amphetamines cause a rise in T4, but no one has pursued this line of research in some time. And no one has shown a definitive link between diet pills and Graves'. It's commonly thought that the initial hypothyroid phase of Graves' disease (usually not diagnosed) causes many people to seek out weight loss methods. About 15% of people with Graves' gain weight instead of losing it. This is more common in younger people and is usually related to the increased appetite seen in hyperthyroidism and food cravings caused by nutrient deficiencies.
Anti-thyroid drugs don't cause weight gain, but they slow down metabolism, restoring it to normal. If the ATD dose is too high, weight gain can occur. If you use the appropriate ATD dose weight gain should be minimal. With ATDs you start out on a moderate dose, and this dose is reduced after 6-8 weeks. Some people who have gained weight end up losing weight on ATDs because they're in better control of their appetite and emotions.
With your levels being fairly high, I'd probably start out with ATDs and once the dose is reduced and your FT4 and FT3 are in range, you could begin substituting herbal meds like Thyrosoothe in place of the ATDs if you're having problems. These products work well but when levels are high it's best to start with meds first. Best, Elaine