This Article Full Text Full Text (PDF) All Versions of this Article: 93/6/2413    most recent Author Manuscript (PDF) Submit a related Letter to the Editor Purchase Article View Shopping Cart Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Google Scholar Articles by Dimitriadis, G. Articles by Raptis, S. A. PubMed PubMed Citation Articles by Dimitriadis, G. Articles by Raptis, S. A. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB GLUCOSE Related Collections Metabolism Thyroid

Insulin-Stimulated Rates of Glucose Uptake in Muscle in Hyperthyroidism: The Importance of Blood Flow

Second Department of Internal Medicine (G.D., P.M., V.L., E.B., N.T., T.E., S.A.R.), Research Institute and Diabetes Center, Athens University Medical School, "Attikon" University Hospital, GR-12462 Haidari, Greece; Hellenic National Center for Research, Prevention and Treatment of Diabetes Mellitus and Its Complications (E.M., S.A.R.), GR-10675 Athens, Greece; Department of Endocrinology (E.K.), Elena Venizelou Hospital, GR-11521 Athens, Greece; and Department of Nutrition Science-Dietetics (D.P.), Harokopio University, GR-17671 Athens, Greece

Address all correspondence and requests for reprints to: George Dimitriadis, M.D., D.Phil., Second Department of Internal Medicine, Research Institute and Diabetes Center, Athens University, Attikon University Hospital, 1 Rimini Street, GR-12462 Haidari, Greece. E-mail: gdimi{at}ath.forthnet.gr; or gdimitr{at}med.uoa.gr.

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 Blood was withdrawn for 360 min from a forearm deep vein and the radial artery for measurements of insulin and glucose.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 µmol 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.