Hyperthyroidism and cation pumps in human skeletal muscle

• Published in: American journal of physiology: endocrinology and metabolism 2005-06, Vol.288 (6), p.E1265-E1269
• Main Authors: Riis, Anne Lene Dalkjaer, Jorgensen, Jens Otto Lunde, Moller, Niels, Weeke, Jorgen, Clausen, Torben
• Format: Article
• Language: English
• Subjects: Adult; Antithyroid Agents - therapeutic use; Biopsy; Calcium-Transporting ATPases - metabolism; Calorimetry, Indirect; Energy Metabolism - physiology; Female; Humans; Hyperthyroidism - drug therapy; Hyperthyroidism - enzymology; Male; Methimazole - therapeutic use; Middle Aged; Muscle, Skeletal - enzymology; Sodium-Potassium-Exchanging ATPase - metabolism
• ISSN: 0193-1849; 1522-1555
• DOI: 10.1152/ajpendo.00533.2004

1 Medical Department M (Endocrinology and Diabetes) and 2 Medical Research Laboratories, Aarhus University Hospital, and 3 Institute of Physiology, University of Aarhus, Aarhus, Denmark Submitted 2 November 2004 ; accepted in final form 6 December 2004 Skeletal muscle constitutes the major target organ for the thermogenic action of thyroid hormone. We examined the possible relation between energy expenditure (EE), thyroid status, and the contents of Ca 2+ -ATPase and Na + -K + -ATPasein human skeletal muscle. Eleven hyperthyroid patients with Graves' disease were studied before and after medical treatment with methimazole and compared with eight healthy subjects. Muscle biopsies were taken from the vastus lateralis muscle, and EE was determined by indirect calorimetry. Before treatment, the patients had two- to fivefold elevated total plasma T 3 and 41% elevated EE compared with when euthyroidism had been achieved. In hyperthyroidism, the content of Ca 2+ -ATPase was increased: (mean ± SD) 6,555 ± 604 vs. 5,212 ± 1,580 pmol/g in euthyroidism ( P = 0.04) and 4,523 ± 1,311 pmol/g in healthy controls ( P = 0.0005). The content of Na + -K + -ATPase showed 89% increase in hyperthyroidism: 558 ± 101 vs. 296 ± 34 pmol/g ( P = 0.0001) in euthyroidism and 278 ± 52 pmol/g in healthy controls ( P < 0.0001). In euthyroidism, the contents of both cation pumps did not differ from those of healthy controls. The Ca 2+ -ATPase content was significantly correlated to plasma T 3 and resting EE. This provides the first evidence that, in human skeletal muscle, the capacity for Ca 2+ recycling and active Na + -K + transport are correlated to EE and thyroid status. Ca 2+ -activated adenosine triphosphatase; Na + -K + -activated adenosine triphosphatase; energy expenditure Address for reprint requests and other correspondence: A. L. D. Riis, Medical Dept. M, Aarhus Univ. Hospital, 8000 Aarhus C, Denmark (E-Mail: anne.lene.riis{at}ki.au.dk )