The radiation dose to the thyroid during a mammogram is extremely low (less than 1% of the dose received by the breast).

This is equivalent to 30 minutes of exposure to radiation received from natural sources (for example, half an hour of sun on the beach).

Thus, the risk of inducing thyroid cancer after a mammogram is negligible (less than 1 case in every 17 million women who undergo annual mammography between 40 and 80 years of age)
Furthermore, the thyroid shield may make mammography difficult to perform (positioning) and lead to the need for repeat examinations.

Therefore, the Sociedade Brasileira de Mastologia, Colégio Brasileiro de Radiologia and Federação Brasileira das Associações de Ginecologia e Obstetrícia do not recommend the use of thyroid shield for mammography examinations.