When you have an overactive thyroid, also known as hyperthyroidism or thyrotoxicosis, your thyroid gland produces too much of the thyroid hormones. When these hormone levels are too high, you can have mood swings and weight loss.
Your thyroid gland uses a chemical called iodine to produce these hormones. Carbimazole blocks the way your body processes iodine and reduces the amount of thyroid hormones produced. This can then help your symptoms.