AJP - Endocrinology and Metabolism, Vol 247, Issue 5 681-E687, Copyright © 1984 by American Physiological Society
Triiodothyronine increases splanchnic release and peripheral uptake of glucose in healthy humans
P. R. Bratusch-Marrain, S. Gasic and W. K. Waldhausl
To examine the effect of experimental hyperthyroidism induced by
triiodothyronine (T3) administration on glucose utilization and
glucose-stimulated insulin secretion, euglycemic insulin clamp studies (A),
hyperglycemic clamp studies (B), and estimation of splanchnic glucose
metabolism after an oral glucose load by means of the hepatic venous
catheter technique (C) were performed in healthy volunteers whose serum T3
concentration had been increased from 1.1 +/- 0.02 (SE) to 3.5 +/- 0.2
ng/ml. At plasma insulin concentrations of 77 +/- 6 microU/ml and
maintenance of euglycemia, insulin-mediated glucose metabolism (6.8 +/- 0.4
mg X kg-1 X min-1) was not significantly altered following T3 exposure (7.2
+/- 0.7) in study A. When plasma glucose was raised and maintained at 7
mmol/l above basal, glucose uptake (10.6 +/- 0.7 mg X kg-1 X min-1) was
increased to 14.6 +/- 2.0 mg X kg-1 X min-1 (P less than 0.02) following T3
administration in study B. In study C, basal splanchnic glucose output (104
+/- 10 mg/min) was markedly augmented when preceded by T3 exposure (167 +/-
17 mg/min; P less than 0.005). After a 75-g glucose load, splanchnic
glucose output was enhanced by T3 by 30% (43.4 +/- 2.2 vs. 56.9 +/- 6.6
g/150 min; P less than 0.05), whereas arterial plasma concentrations of
glucose, insulin, and C-peptide were not significantly different. It is
concluded that in healthy humans, exposure to elevated plasma
concentrations of T3 increases the amount of glucose to be released from
the splanchnic bed. Glucose tolerance, however, remains unaltered, because
peripheral glucose uptake is increased at the same time.
