Quantitative study of the thyrotropic activity of anterior pituitary extracts

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Abstract
The thyrotropic activity of anterior pituitary extracts was tested by their capacity to increase the wt. of the thyroids in 38 immature $ guinea pigs, of 150-300 gm. (av. 200 gm.) body wt., and 31 mgm. av. wt. of thyroids, which grow at the rate of 1 mgm. per 6 gm. body wt. The max. increase produced by constant daily dose of anterior lobe extract is attained in 8-10 days. The standard period of injection in these exps. was 5 days, the largest thyroids produced in this time having an av. wt. of 101 mgm. in a group of 5 animals. Thyroids caused to enlarge to 80 mgm. return to normal size ca. 3 wks. after the last injection. A curve for response/dose for standardizing extracts, was made on groups of 10 animals and, pending some international agreement, the unit adopted for the laboratory is the thyrotropic activity contained in an amt. of extract which, given daily for 5 days, will cause the thyroids of the 200 gm. guinea-pig to attain a wt. of 60 mgm., i.e., ca. double the normal. The efficiency of some of the methods commonly used in the preparation of thyrotropic extracts is examined in the light of these quantitative observations.