Dr Mark Vanderpump, Consultant Endocrinologist at the Royal Free Hospital in London and President of the British Thyroid Association has given the following advice:

'For people with a properly functioning thyroid iodine is essential as it is required for the production of thyroxine. It is particularly important in women who are pregnant as it is needed to ensure the development of a baby's brain during pregnancy and early life. People who are taking replacement thyroxine (levothyroxine) however do not have a functioning thyroid to absorb iodine and therefore iodine is not required. For patients being treated for hyperthyroidism, taking an iodine supplement is unnecessary and can worsen the condition.'