Myopathy as the Persistently Isolated Symptomatology of Primary Autoimmune Hypothyroidism

Abstract

Although disorders of thyroid function may cause a wide range of muscle disturbances, an overt myopathy has been rarely reported as an isolated clinical presentation of hypothyroidism. We observed 10 patients (5 males and 5 females) who had been referred to the department of neurology because of muscular fatigability, myalgia, cramps, or proximal weakness. Laboratory investigation showed that all patients had hypothyroidism due to Hashimoto's thyroiditis (atrophic variant in 9/10). Classic symptoms/signs of hypothyroidism such as lethargy, constipation, cold intolerance, myxedematous facies, and/or bradycardia were absent, as assessed independently by the three coauthoring thyroidologists. Muscular complaints improved greatly and then disappeared after substitutive levothyroxine treatment. Muscle biopsy revealed nonspecific changes. Nicotinamide adenine dinucleotide reductase (NADH-TR)-hyporeactive cores were present in two patients (10% and 90% of type 1 fibers). On electron microscopy, the core areas showed disorganized myofibrils, Z-band streaming, rod formation, and paucity of mitochondria and glycogen granules. Desmin intermediate filaments were overexpressed only in some cores. The similarity of the pattern of desmin expression between hypothyroid cores and target lesions of denervated fibers supports the hypothesis that, at least in some of our patients, myopathy was the result of an impaired nerve-mediated action of thyroid hormones on skeletal muscle. Our observations suggest that an isolated myopathy as the sole manifestation of hypothyroidism is not a rare event. We postulate that our cases may constitute a peculiar subgroup of Hashimoto's thyroiditis patients: (1) the strikingly abnormal F/M ratio of 1:1; (2) the relatively younger age; (3) the rarity of the goitrous variant; (4) the unusual finding of antithyroglobulin (Tg-Ab) > antithyroid peroxidase (TPO-Ab). Thorough evaluation of thyroid function is appropriate in patients with myopathy of uncertain origin.

Serum CXCL10 levels and neuromuscular manifestations in patients with autoimmune thyroid diseases

“…Typical symptoms in hypothyroidism include usually proximal muscle weakness, stiffness, cramps, myalgia, and muscle fatigue [28]. Myopathy may be the sole clinical manifestation of hypothyroidism [29]. Physical examination may reveal evidence of proximal muscle weakness, hypokinesis, and delayed relaxation of the deep tendon reflexes.…”

“…Physical examination may reveal evidence of proximal muscle weakness, hypokinesis, and delayed relaxation of the deep tendon reflexes. The patients may have symptoms and signs of mononeuropathy, polyneuropathy, or cranial nerve neuropathy [29]. In essence, the most common mononeuropathy encountered in hypothyroid patients is the CTS associated with median nerve compression as it traverses the volar aspect of the wrist.…”

Granulomatous myositis associated with antithyroglobulin and antithyroid peroxidase antibodies

“…GM has been reported in association with thymoma and myasthenia gravis, and rarely with thyroid dysfunction but elevated thyroid autoantibody levels have not been reported so far. In this context it is noteworthy that in muscle biopsies of patients with primary autoimmune hypothyroidism there is no evidence of inflammatory infiltrates or generalised MHC I antigen expression and the myopathy improves with levothyroxine treatment [4]. In contrast, our patient had some striking similarities to patients with Hashimoto's encephalitis, who are usually euthyroid, have elevated thyroid antibodies, have a CD 3+ infiltrate and respond to immunosuppressive treatment suggesting an autoimmune pathogenesis [5].…”

“…Apart from a 2 year history of psoriasis, treated with methotrexate (30 mg/week), his medical history was unremarkable. Neurological examination demonstrated symmetrical shoulder girdle and neck extensor muscle weakness (MRC grade [3][4] resulting in a head-drop, as well as milder weakness of proximal lower limb muscles (grade 4-). Laboratory testing revealed elevated CK (200 U/l), ESR (30/50), and peroxidase antibodies (TPO/MAK-Ab: 221 U/l, normal: < 10) and antithyroglobulin antibodies (Tg/TAK-Ab: 69 U/l, normal: < 10) but normal T3, T4 and TSH levels.…”

Clinicopathological Conference Weakness in the Kneesx

“…Hypothyroidism is associated with a syndrome of proximal muscle weakness, muscle cramps, and stiffness. 25 In hypothyroidism the patient often has an elevated CPK, and a classic finding on physical exam is a slow relaxation phase of the DTR. Hyperthyroidism can also cause a syndrome of proximal muscle weakness.…”