The effect of 3,5,3'-triiodothyronine or thyrotropin-releasing hormone on pituitary hormone responses to arginine infusions in hypothyroid patients.
Serum PRL and GH responses to a control arginine infusion were determined in seven hypothyroid patients. During the infusion, basal TSH levels fell slightly but significantly. On a following day, a second arginine infusion was performed, 5 min after iv injection of 500 micrograms TRH. The mean peak PRL response was enhanced 6-fold and occurred earlier, while the mean peak GH response remained unaffected. Mean peak TSH levels were only 128% above baseline after TRH. On a third day, a third arginine infusion was performed 4 h after oral administration of 100 micrograms T3; mean serum T3 levels were increased from 57 to a peak of 481 ng/dl 5 h after T3. The mean GH response was significantly reduced by 71% at 90 min, with an overall reduction of the GH output of 47%, while the PRL response remained unaffected. Thus, acute elevation of serum T3 levels in hypothyroidism appear to inhibit the mean GH response to arginine.
D000328:Adult; D000368:Aged; D001120:Arginine; D005260:Female; D013006:Growth Hormone / Q000097:blood; D006801:Humans; D007037:Hypothyroidism / Q000097:blood*; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D010908:Pituitary Hormones, Anterior / Q000097:blood*; D011388:Prolactin / Q000097:blood; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone; D014284:Triiodothyronine / Q000097:blood
D010908:Pituitary Hormones, Anterior; D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D013972:Thyrotropin; D013006:Growth Hormone; D001120:Arginine