The international standard for thyrotrophin.

In 1953, the Department of Biological Standards, National Institute for Medical Research, London, was authorized by the WHO Expert Committee on Biological Standardization to proceed with the establishment of an International Standard for Thyrotrophin. A number of laboratories were requested to assist in the collaborative study of the proposed new standard, and those which agreed were sent a short note (annexed to the paper) explaining the basis of the study. In this paper, the authors describe the assay methods used by ten laboratories and discuss the results obtained.