False hyperthyrotropinemia induced by heterophilic antibodies against rabbit serum

A case of false hyperthyrotropinemia was investigated. The serum of the patient contained heterophilic antibodies against rabbit immunoglobulins secondary to immunization with rabbit serum. Some vaccines against viral or bacterial diseases contain animal serum capable of inducing heterophilic antibodies in man. This technical problem can be prevented by the routine addition of control rabbit serum or immunoglobulins to the TSH RIA.