In pregnancy and other states of increased levels of female hormones in blood (e.g. administration of birth control pills and estrogen replacement), and in infections; thyroid binding globulin (which is a special type of body protein that binds the thyroid hormones in blood) may be elevated. This may result in elevation of total thyroid hormone levels when a pregnancy blood testing is done for routine check-up. However, the form of thyroid hormones that is active (the one that produces effects), is not elevated. Therefore, treatment is usually not needed.

Therefore, if some female is pregnant, and her total thyroid hormone levels are found raised, it is better to get a repeat testing done to know the levels of TSH (thyroid stimulating hormone), and free thyroid hormone than reaching to a conclusion of having hyperthyroidism.