Characterization of the pituitary response in the TRH test by kinetic modeling.

Applying the principles of chemical kinetics to the time course of TSH concentrations after TRH infusion, individual values for total TSH release from the pituitary, TSH elimination and release rates, and latency for TSH release were found for 40 patients. Justification for using the observed peak TSH elevation as a consistent reflection of the total TSH release was provided by the high correlation between these two (r = 0.97, P less than 0.001). Kinetic modeling indicated that the most consistent reflection of total pituitary TSH response is the TSH elevation over baseline 35 min after TRH (with the peak expected 30 min post-TRH), rather than the area under the curve.