STUDIES ON HUMAN GROWTH HORMONE. I. A RADIO-IMMUNOASSAY FOR HUMAN GROWTH HORMONE*

Abstract

Methods for the radioiodination of human growth hormone which yield labeled hormone of both high specific radioactivity and reactivity with specific antibodies are described. With these preparations, a radio-immunoassay for human growth hormone, capable of detecting 3 to 6 mug human growth hormone, has been developed. Bovine, ovine, and porcine growth hormone did not prevent the immunoprecipitation of iodinated human growth hormone in this assay, but monkey growth hormone inhibited iodinated human growth hormone precipitation. Human and animal sera were found to contain a nonspecific inhibitor of the immunoassay system which can be excluded by an extraction procedure that permits the extraction of growth hormone. Circulating levels of growth hormone determined by radio-immunoassay in normal adults ranged from 0 to 50 mug per ml. Levels of 15 to 250 m[mu]g per ml were found in a series of untreated acromegalic subjects while values after treatment ranged from 0 to 27 m[mu]g per ml.