Insulin-stimulated rates of glucose uptake in muscle in hyperthyroidism: the importance of blood flow.
BACKGROUND
In hyperthyroidism, although hepatic insulin resistance is well established, information on the effects of insulin on glucose uptake in skeletal muscle is variable.


METHODS
To investigate this, a meal was given to nine hyperthyroid (HR) and seven euthyroid (EU) subjects. Blood was withdrawn for 360 min from a forearm deep vein and the radial artery for measurements of insulin and glucose. Forearm blood flow (BF) was measured with strain-gauge plethysmography. Glucose flux was calculated as arteriovenous difference multiplied by BF and fractional glucose extraction as arteriovenous difference divided by arterial glucose concentrations.


RESULTS
Both groups displayed comparable postprandial glucose levels, with the HR having higher insulin levels than the EU. In the forearm of HR vs. EU: 1) glucose flux was similar [area under the curve (AUC)(0-360) 673 +/- 143 vs. 826 +/- 157 micromol per 100 ml tissue]; 2) BF was increased (AUC(0-360) 3076 +/- 338 vs. 1745 +/- 145 ml per 100 ml tissue, P = 0.005); and 3) fractional glucose extraction was decreased (AUC(0-360) 14.5 +/- 3 vs. 32 +/- 5%min, P = 0.03).


CONCLUSIONS
These results suggest that, in hyperthyroidism, insulin-stimulated glucose uptake in muscle is impaired; this defect is corrected, at least in part, by the increases in BF.
Dimitriadis
George
G
Second Department of Internal Medicine, Research Institute and Diabetes Center, Athens University, Attikon University Hospital, 1 Rimini Street, Haidari, Greece. gdimi@ath.forthnet.gr
Mitrou
Panayota
P
Lambadiari
Vaia
V
Boutati
Eleni
E
Maratou
Eirini
E
Koukkou
Eftychia
E
Panagiotakos
Demosthenes
D
Tountas
Nikos
N
Economopoulos
Theofanis
T
Raptis
Sotirios A
SA
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D005215:Fasting / Q000097:blood; D005260:Female; D005542:Forearm / Q000098:blood supply; D005947:Glucose / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D006980:Hyperthyroidism / Q000378:metabolism*; D007328:Insulin / Q000032:analysis / Q000494:pharmacology*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism*; D017534:Radial Artery / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology
D001786:Blood Glucose; D007328:Insulin; D005947:Glucose