There is no lower age limit. If the child has the RET mutation for MEN2b then a thyroidectomy should be done regardless of the calcitonin status. Refer to American Thyroid Association Guidelines Task Force, Kloos RT, Eng C, Evans B, Francis GL, Gagel RF, Gharib H, Moley JF, Pacini F, Ringel MD, Schlumberger M, Wells SA Jr: Medullary thyroid cancer: management guidelines of the American Thyroid Association.
According to the American Thyroid Association, prophylactic thyroidectomy is recommended for MEN2A paediatric patients genetically diagnosed. The age of recommended thyroidectomy varies according to the codon mutation present.