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

• Published in: The journal of clinical endocrinology and metabolism Vol. 93; no. 6; pp. 2413 - 2415
• Main Authors: Dimitriadis, George, Mitrou, Panayota, Lambadiari, Vaia, Boutati, Eleni, Maratou, Eirini, Koukkou, Eftychia, Panagiotakos, Demosthenes, Tountas, Nikos, Economopoulos, Theofanis, Raptis, Sotirios A.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Endocrine Society 01-06-2008; Copyright by The Endocrine Society
• Subjects: Adult; Biological and medical sciences; Blood Glucose - analysis; Endocrinopathies; Fasting - blood; Feeding. Feeding behavior; Female; Forearm - blood supply; Fundamental and applied biological sciences. Psychology; Glucose - analysis; Glucose - metabolism; Humans; Hyperthyroidism - metabolism; Insulin - analysis; Insulin - pharmacology; Male; Medical sciences; Muscle, Skeletal - blood supply; Muscle, Skeletal - drug effects; Muscle, Skeletal - metabolism; Non tumoral diseases. Target tissue resistance. Benign neoplasms; Radial Artery - chemistry; Radial Artery - drug effects; Radial Artery - physiology; Regional Blood Flow - physiology; Thyroid. Thyroid axis (diseases); Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vertebrates: endocrinology; Endocrinopathy; Obesity; Pancreatic hormone; Nutrition; Hyperthyroidism; Rate; Thyroid diseases; Nutrition disorder; Metabolic diseases; Glucose; Insulin; Uptake; Blood flow; Muscle; Hemodynamics; Endocrinology; Nutritional status
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2007-2832

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 Blood was withdrawn for 360 min from a forearm deep vein and the radial artery for measurements of insulin and glucose.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 (AUC0–360 3076 ± 338 vs. 1745 ± 145 ml per 100 ml tissue, P = 0.005); and 3) fractional glucose extraction was decreased (AUC0–360 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.