Effect of synthetic thyrotropin-releasing factor (TRF) on pituitary TSH secretion in man.

Abstract

Synthetic thyrotropin-releasing factor (TRF), L-pyroglutamyl-L-histidil-L-prolineamide, has been administered intravenously to 35 cases of normal or suspected pituitary insufficient volunteers in doses ranging from 25 to 200μg. Changes of plasma TSH levels, PBI and T3 resin sponge uptake (T3RSU) were estimated. TRF in doses of 25-200 μg stimulates a rapid rise in plasma TSH in all of the 13 normal subjects. 3 out of 5 normal subjects showed rise in serum PBI while T3RSU remained unchanged. The only side effect was transient nausea in several cases. No or slight rise in plasma TSH levels occurred followine 100μg of TRF in patients with pituitary chromophobe adenoma and craniopharyngioma who had a longstanding pituitary insufficiency and low level of thyroid function. However, certain cases of both tumor showed almost normal TSH response to TRF. It was also noticed that no TSH response to TRF was observed in two hyperthyroid patients and one medicated with thyroid powder. Normal TSH increase following TRF was obtained from cases with suspected hypotituitarism, diabetes insipidus, arachnoiditis of chiasma region, myotonic dystrophy and a 77 years-old female. Suboptimal response were observed in a patient with suspected Cushing' syndrome. It is concluded that synthetic TRF is useful for testing the pituitary TSH reserve in man. Plasma TSH response to TRF in various clinical conditions was discussed.