The effect of intramuscular thyrotropin-releasing hormone on the thyroid 131I uptake in man

The effect of a single large intramuscular injections of TRH (2 mg) on the thyroid 131I uptake in normal man was assessed at varying intervals following the administration of TRH. When the 131I was given simultaneously with TRH, the 3- and 5-hour 131I uptake decreased. When the 131I was administered 8 hours after TRH, the thyroid 131I increased significantly. This response in uptake is similar to that observed in the rat following TSH stimulation. The present study defines the time course of the thyroid 131I uptake response to endogenous TSH stimulation.