Abstract
SUMMARY: Using McKenzie's [1958b] modification of Adams & Purves's [1955] method for bioassay of thyrotrophin, which depends on the release into the circulating blood of radio-iodine from thyroid glands of mice, an attempt was made to measure thyrotrophin in human serum. Two types of response were encountered. The first, characteristic of hypothyroidism, resulted in a peak increase in blood radioactivity 2 hr after injection and resembles the response to standard thyrotrophin preparations. The second response, characteristic of hyperthyroidism, was delayed and the blood radioactivity did not reach a peak until 12 hr after the serum injection. The incidence of the two types of response has been investigated and several additional differences between the delayed response and the response to thyrotrophin extracted from pituitary tissue have been established.