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Whole body and forearm substrate metabolism in hyperthyroidism: evidence of increased basal muscle protein breakdown.
Am J Physiol Endocrinol Metab. 2005 Jun; 288(6):E1067-73.AJ

Abstract

Thyroid hormones have significant metabolic effects, and muscle wasting and weakness are prominent clinical features of chronic hyperthyroidism. To assess the underlying mechanisms, we examined seven hyperthyroid women with Graves' disease before (Ht) and after (Eut) medical treatment and seven control subjects (Ctr). All subjects underwent a 3-h study in the postabsorptive state. After regional catheterization, protein dynamics of the whole body and of the forearm muscles were measured by amino acid tracer dilution technique using [15N]phenylalanine and [2H4]tyrosine. Before treatment, triiodothyronine was elevated (6.6 nmol/l) and whole body protein breakdown was increased 40%. The net forearm release of phenylalanine was increased in hyperthyroidism (microg.100 ml(-1).min(-1)): -7.0 +/- 1.2 Ht vs. -3.8 +/- 0.8 Eut (P = 0.04), -4.2 +/- 0.3 Ctr (P = 0.048). Muscle protein breakdown, assessed by phenylalanine rate of appearance, was increased (microg.100 ml(-1).min(-1)): 15.5 +/- 2.0 Ht vs. 9.6 +/- 1.4 Eut (P = 0.03), 9.9 +/- 0.6 Ctr (P = 0.02). Muscle protein synthesis rate did not differ significantly. Muscle mass and muscle function were decreased 10-20% before treatment. All abnormalities were normalized after therapy. In conclusion, our results show that hyperthyroidism is associated with increased muscle amino acid release resulting from increased muscle protein breakdown. These abnormalities can explain the clinical manifestations of sarcopenia and myopathy.

Authors+Show Affiliations

Medical Dept. M, Aarhus Univ. Hospital, DK-8000 Aarhus C, Denmark. anne.lene.riis@ki.au.dkNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15657093

Citation

Riis, Anne Lene Dalkjaer, et al. "Whole Body and Forearm Substrate Metabolism in Hyperthyroidism: Evidence of Increased Basal Muscle Protein Breakdown." American Journal of Physiology. Endocrinology and Metabolism, vol. 288, no. 6, 2005, pp. E1067-73.
Riis AL, Jørgensen JO, Gjedde S, et al. Whole body and forearm substrate metabolism in hyperthyroidism: evidence of increased basal muscle protein breakdown. Am J Physiol Endocrinol Metab. 2005;288(6):E1067-73.
Riis, A. L., Jørgensen, J. O., Gjedde, S., Nørrelund, H., Jurik, A. G., Nair, K. S., Ivarsen, P., Weeke, J., & Møller, N. (2005). Whole body and forearm substrate metabolism in hyperthyroidism: evidence of increased basal muscle protein breakdown. American Journal of Physiology. Endocrinology and Metabolism, 288(6), E1067-73.
Riis AL, et al. Whole Body and Forearm Substrate Metabolism in Hyperthyroidism: Evidence of Increased Basal Muscle Protein Breakdown. Am J Physiol Endocrinol Metab. 2005;288(6):E1067-73. PubMed PMID: 15657093.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Whole body and forearm substrate metabolism in hyperthyroidism: evidence of increased basal muscle protein breakdown. AU - Riis,Anne Lene Dalkjaer, AU - Jørgensen,Jens Otto Lunde, AU - Gjedde,Signe, AU - Nørrelund,Helene, AU - Jurik,Anne Grethe, AU - Nair,K S, AU - Ivarsen,Per, AU - Weeke,Jørgen, AU - Møller,Niels, Y1 - 2005/01/18/ PY - 2005/1/20/pubmed PY - 2005/6/17/medline PY - 2005/1/20/entrez SP - E1067 EP - 73 JF - American journal of physiology. Endocrinology and metabolism JO - Am J Physiol Endocrinol Metab VL - 288 IS - 6 N2 - Thyroid hormones have significant metabolic effects, and muscle wasting and weakness are prominent clinical features of chronic hyperthyroidism. To assess the underlying mechanisms, we examined seven hyperthyroid women with Graves' disease before (Ht) and after (Eut) medical treatment and seven control subjects (Ctr). All subjects underwent a 3-h study in the postabsorptive state. After regional catheterization, protein dynamics of the whole body and of the forearm muscles were measured by amino acid tracer dilution technique using [15N]phenylalanine and [2H4]tyrosine. Before treatment, triiodothyronine was elevated (6.6 nmol/l) and whole body protein breakdown was increased 40%. The net forearm release of phenylalanine was increased in hyperthyroidism (microg.100 ml(-1).min(-1)): -7.0 +/- 1.2 Ht vs. -3.8 +/- 0.8 Eut (P = 0.04), -4.2 +/- 0.3 Ctr (P = 0.048). Muscle protein breakdown, assessed by phenylalanine rate of appearance, was increased (microg.100 ml(-1).min(-1)): 15.5 +/- 2.0 Ht vs. 9.6 +/- 1.4 Eut (P = 0.03), 9.9 +/- 0.6 Ctr (P = 0.02). Muscle protein synthesis rate did not differ significantly. Muscle mass and muscle function were decreased 10-20% before treatment. All abnormalities were normalized after therapy. In conclusion, our results show that hyperthyroidism is associated with increased muscle amino acid release resulting from increased muscle protein breakdown. These abnormalities can explain the clinical manifestations of sarcopenia and myopathy. SN - 0193-1849 UR - https://www.unboundmedicine.com/medline/citation/15657093/Whole_body_and_forearm_substrate_metabolism_in_hyperthyroidism:_evidence_of_increased_basal_muscle_protein_breakdown_ DB - PRIME DP - Unbound Medicine ER -