All of the following statements regarding iodides are true, except:

Iodides shut off the release of the preformed thyroid hormones. It is the quickest acting drug hence used to control the hyperthyroidism in thyrotoxic crisis. It makes the gland firm and less vascular hence used before thyroid surgery. It produces maximum clinical benefit within 10-14 days. They can cross the placenta and can cause cretinism in the fetus hence to be avoided during pregnancy.