When people with Graves’ disease get their thyroid levels back to normal, their cholesterol might get worse because the overactive thyroid was hiding a cholesterol problem all along.

If someone already has high cholesterol and then gets an overactive thyroid from Graves’ disease, their cholesterol might temporarily get better — making it harder to notice the original problem.

Sometimes people can have Graves’ disease and show symptoms like bulging eyes or skin issues even if their thyroid isn’t overactive—this can happen if their thyroid doesn’t work well enough to produce excess hormones, and it means doctors might miss the disease if they only check thyroid levels.

Your thyroid hormones help your body clear 'bad' cholesterol from the blood by turning up a cleanup system. That’s why people with an overactive thyroid tend to have lower bad cholesterol, and those with an underactive thyroid often have higher levels.