Actions of thyrotropin-releasing-hormone on gastrointestinal function in man. I. Inhibition of glucose and xylose absorption from the gut.

We studied serum glucose levels following a peroral glucose test in 6 healthy subjects on 2 alternate days in random order; with or without an i.v. TRH infusion for 3 hours (0.66 mg/hour). TRH infusion reduced serum glucose levels following oral glucose in all 6 subjects investigated. Serum insulin levels were reduced accordingly. Furthermore, serum xylose levels following peroral xylose were studied in the same 6 subjects. TRH infusion i.v. reduced serum xylose levels in all 6 subjects studied. I.v. glucose tolerance tests with or without an i.v. TRH infusion (0.66 mg/h) for 3 hours were studied in 4 healthy subjects. No change in serum glucose or insulin levels following TRH infusion was observed. We conclude that an i.v. infusion of TRH reduces serum levels of glucose following a peroral glucose load and serum xylose levels following a peroral xylose load. TRH thus has marked actions on gastro-intestinal function in man inhibiting and/or retarding the absorption of glucose and xylose from the gut.