ABSTRACT
The effects of the administration of normal saline in four normal subjects and the single iv injections of synthetic pyroglutamyl-histidyl-proline amide (TRH) in doses of 6.25, 12.5, 25, 50, 100, 200 and 400 μg in 12 healthy subjects were evaluated by clinical observations and serial measurements from −10 to + 360 minutes of serum TSH, PBI, STH, cholesterol, glucose and insulin.
Normal saline and TRH 6.25 μg iv did not change the serum TSH level. The minimum iv dose of TRH increasing serum TSH within 10 minutes was 12.5 μg. Nine of 12 subjects gave maximal increases of serum TSH after TRH 100 μg and all after 200 and 400 μg. The time for the peak response varied with the dose from 15 to 60 minutes. The dose-response curves, average and individual, were complex and not linear. This was interpreted as a varying degree of stimulation of both pituitary synthesis and release of TSH by TRH.
PBI changes were measured at 2 h and 6 h. Minimum dose for a significant increase of PBI was 12.5 μg and 6.25 μg of TRH for the respective times.
No change in basal STH-levels occurred in 53 of 65 TRH-stimulation tests. Nine of the 12 changes in serum STH occurred in four subjects with varying basal STH-levels. No changes were found in serum cholesterol, glucose or insulin.
Our results show that 50 μg of TRH can be used as a standard dose for the single iv stimulation of pituitary release of TSH. TRH stimulated both TSH and STH release in 18% of our tests.
