Energetic metabolism in hypothyroid skeletal muscle, as studied by phosphorus magnetic resonance spectroscopy.

Abstract

Phosphorus nuclear magnetic resonance spectroscopy was used to investigate the muscle bioenergetics in different hypothyroid states. Using the thenar muscle group as reference, 2 patients with chronic and severe hormonal deficiency, 3 patients with subacute hypothyroidism, and 8 patients with moderate thyroid insufficiency with isolated high blood TSH levels were studied at rest, during exercise, and during subsequent recovery. The patients were compared with 15 control subjects. Only 1 patient presented a clinical myopathy. The intracellular pH and the relative measurements of inorganic phosphate, phosphocreatine, phosphodiesters, and ATP were directly calculated from phosphorus spectra. Resting muscle showed a significant rise in the inorganic phosphate to ATP ratio. In working hypothyroid muscle, a more important decrease in phosphocreatine levels was noted in patients with chronic and subacute thyroid deficiency, while the intracellular pH fall was greater in all hypothyroid patients than in control subjects. The phosphocreatine recovery rate was lower in all deficient patients, reflecting a probable mitochondrial metabolism impairment. These results are consistent with a defect of the high energy phosphate metabolism in hypothyroidism, even in moderate or recent hormonal deficiency.

Bio-energetic impairment in human calf muscle in thyroid disorders: a 31P MRS study

“…Our results are consistent with earlier MRS as well as enzyme based findings, which suggest reduced oxidative metabolism in hypothyroids [3][4][5]27]. However, none of the earlier studies have used PCr recovery rate to estimate oxidative capacity of the muscle in hypothyroids.…”

“…Resting muscle demonstrated a low PCr/Pi ratio and increased Pi concentration. The abnormal increase in [Pi] in hypothyroid muscle is the most frequent cause of a low PCr/Pi at rest and mitochondrial dysfunction has been suggested as an explanation of this rise in Pi during resting condition [3]. Thyroid hormones have been recognized as major regulators of oxidative energy metabolism at the levels of the mitochondrion.…”

“…Therefore, clinically significant changes in skeletal mass and function occur in hypo as well as hyperthyroidism. Mitochondrial metabolism particularly oxidative phosphorylation is said to be altered in both hypothyroid and thyrotoxic state [3][4][5]. However, muscle impairment along with energy metabolism improves dramatically after correction of thyroid dysfunction [5,6].…”

Effects of subclinical hypothyroidism treatment on psychiatric symptoms, muscular complaints, and quality of life

“…Neuromuscular manifestations are well established in overt hypothyroidism (OH), and impaired muscle function is frequently observed (1,2). Thyroid hormone deficiency may also interfere substantially with various aspects of physical, mental and social well-being (3).…”

Impact of Overt and Subclinical Hypothyroidism on Exercise Tolerance: A Systematic Review

“…They showed muscle fiber and mitochondrial staining abnormalities in untreated patients with OVH (Siciliano et al, 2002). In these patients, an impairment of extra-mitochondrial energy supply was found at rest and during exercise as compared with control muscle (Kaminsky et al, 1992;Taylor, Rajagopalan, & Radda, 1992). Phosphocreatine (PCr) and intracellular pH (pHi) recovery rates after exercise were similar or slower in patients with OVH as compared with controls (Kaminsky et al, 1992;Rana et al, 2012;Taylor et al, 1992).…”