Thyroid hormone deficiency and muscle metabolism during light and heavy exercise in dogs

Abstract

Muscle glycogen, glycolytic intermediate and high energy phosphate contents were compared in 5 intact-control (C) and thyroidectomized (THY) dogs after 30 min treadmill exercise of low (40W) and high (70W) intensities. Although after the exercise of relatively low intensity the rate of glycogenolysis and muscle lactate accumulation in THY dogs exceeded those in controls, the diminished oxidative capacity in the former was inadequately compensated, resulting in lowering of APT and CrP contents. At the higher work load the latter effects were more pronounced while the rate of glycogenolysis was similar or even lower than in controls. Inadequate fuel utilization may be considered as a factor limiting ability for heavy exercise in hypothyroidism.

Clinical and Biochemical Features of Muscle Dysfunction in Subclinical Hypothyroidism

“…Abnormal accumulation of lactate has been reported in hypothyroid dog muscles during exercise (20), but similar results in patients with overt hypothyroidism have not, to our knowledge, been reported. Nuclear magnetic resonance studies in working hypothyroid human and rat muscles (3,4) have documented a decreased intracellular pH during muscle exercise.…”