Bromide is a common food additive and pesticide that is known to be an endocrine disruptor (exogenous substances that act like hormones in the endocrine system and disrupt the physiologic function of endogenous hormones). It is also a halide, meaning that it competes for the same receptors that the thyroid gland uses to capture the iodine that is essential for the production of vital thyroid hormones and thus contribute to hypothyroidism. Bromide is most commonly found in the form of methyl bromide, a common pesticide used on strawberries; as brominated vegetable oil which is often added to citrus drinks and asthma inhalers; as a fire retardant in fabrics and mattresses; and as potassium bromate, a dough conditioner found in commercial bakery products and some flours.
Source: NaturalTthyroid Choices