Longitudinal study of the effects of chronic hypothyroidism on skeletal muscle in dogs

Abstract

Chronic, experimentally induced hypothyroidism resulted in substantial but subclinical phenotypic myopathic changes indicative of altered muscle energy metabolism and depletion of skeletal muscle carnitine. These abnormalities may contribute to nonspecific clinical signs, such as lethargy and exercise intolerance, often reported in hypothyroid dogs.

Canine hypothyroidism: A review of aetiology and diagnosis

“…These data are largely compiled from Panciera (1994a) and been associated with exercise-induced hyperkalaemia, largely explained by a reduction of the Na þ -K þ -ATPase capacity in the skeletal muscle pool that may contribute to decreased contractile performance and endurance (Schaafsma et al 2002). Additionally, where experimental hypothyroidism did not result in neuropathy, it did result in subclinical, biochemical, electrophysiological and morphological evidence of myopathy (Rossmeisl et al 2009). …”

“…Approximately 20-35% of cases have a mild increased activity of circulating creatine kinase. Whilst often attributable to decreased metabolism or excretion, it may result from the myopathy described in hypothyroidism (Rossmeisl et al 2009). Concentrations of circulating fructosamine are significantly increased, presumably as a result of 108 New Zealand Veterinary Journal 59(3), 2011 Mooney decreased turnover of protein Reusch et al 2002).…”

Tetraparesis, Hemiparesis, and Ataxia

“…Dogs may have signs of diffuse LMN dysfunction, peripheral or central vestibular dysfunction, 609,610 encephalopathy, 611,612 and cranial nerve dysfunction (VII, VIII, IX, X). 575,[605][606][607] The diagnosis is confirmed by reduced free and total serum thyroxine levels, with an elevation in thyroid-stimulating hormone levels. 575 The paresis may vary in symmetry and involve one limb or all limbs.…”

“…189 Hypothyroid Neuropathy. 606,607 Underlying pathophysiologic mechanisms for hypothyroid neuropathy include impaired energy metabolism of the motor neuron and alterations in microtubule assembly and axonal transport. 376,575,[603][604][605][606] Nerve pathology involves both the axon and myelin.…”

“…893 Signs develop between 6 weeks and 7 months of age and are generally much less severe than those in the X-linked dystrophy. 606,902 Distal Myopathy of Rottweilers. These dog often show adduction of the hock and carpal joints.…”