The international reference preparation of calcitonin, human, for bioassay: assessment of material and definition of the international unit.

An international reference material is required for bioassays of preparations of synthetic human calcitonin for administration to man and for use in immunoassays. A preparation of synthetic human calcitonin in ampoules coded 70/234 (previously widely used as the MRC Research Standard) has been examined in an international collaborative study involving 7 laboratories in 6 countries. The results of 34 in vivo bioassays with two other preparations of synthetic human calcitonin showed that this preparation was suitable to serve as a standard. With the agreement of the participants in the collaborative study, the batch of ampoules, code 70/234, was established in 1978 by the World Health Organization as the International Reference Preparation of Calcitonin, Human, for Bioassay. The International Unit of human calcitonin was defined as the activity contained in one ampoule of this preparation, thus maintaining continuity of the unit of the research standard.