Release of Inorganic Iodine from Thyroid Gland in Initial Phase of TSH Action

Summary

Measurement of inorganic I¹³¹ and PBI¹³¹ in thyroid venous blood obtained by catheterization was performed in 17 dogs to study the early effect of TSH. Following a latent period of about 15 minutes, output of both inorganic I¹³¹ and PBI¹³¹ started to increase sharply. The increased output continued for about 10 hours, and thereafter the thyroid gland started to accumulate inorganic iodine. The inorganic I¹³¹ fraction, represented in the trichloroacetic acid supernatant fraction, was confirmed by radiopaperchromatography. TSH apparently releases inorganic iodine, in addition to PBI, from the thyroid in the early phase of its action.