This paper describes the use of screened transfusion plasma as a source of human thyroid stimulating hormone (h-TSH) free protein for standardization of a conventional “double antibody” h-TSH radioimmunoassay. Serum and plasma immunoreactive h-TSH levels have been shown to be stable for up to four days at 4°C and 25°C. A 37°C incubation procedure has been developed which gives an acceptable standard curve, but with some loss of “between batch” precision.
