The glycoprotein hormones, luteinising hormone, follicle-stimulating hormone and TSH, for example, are each composed of two subunits, and the a-subunit is identical in all three hormones. Polyclonal antibodies prepared against one of these glycoprotein hormones will also partially recognise the others; this partial recognition can be measured and expressed as a percentage. A high degree of crossreactivity of the antibody will inevitably result in interference in the immunoassay.
