Hello dear, Garcinia cambogia has been endorsed as an effective weight loss aid, but there are no scientific studies to support it. Similarly there has been no evidence regarding its affect with other medicines, as correctly stated in your post. However, there have been reports of Liver damage/ Hepatotoxicity following the use of Garcinia. So, in my opinion it will not be advisable to use Garcinia as a measure of weight loss. Since you are having a Thyroid problem, weight gain is bound to happen in it. To tackle this, you need to take your Thyroid supplements, perform regular exercise & take certain measures regarding your diet, such as: 1. Avoid eating white breads, rice and pasta. They have high calories and increases the blood sugar level. 2. It is better to have complex carbohydrates such as whole wheat bread, oatmeal and brown rice. 3. Consume low fat versions of milk and cheese and avoid oily foods. 4. Have a diet rich in low calorie protein foods such as egg whites, skinless chicken, fish, etc. 5. It is better to avoid soft drinks and fruit juices which are rich in calories. Instead, drink large amount of water (about 6 to 8 glasses) throughout the day. 6. Dietary fiber such as whole grains, vegetables, fruits, and nuts can also be included in the diet. Wishing you a Good Health. Take care.