Endocrine myopathies

Myopathies of endocrine origin: A review for physicians

Myopathies are a common manifestation of endocrine disorders. Endocrine myopathies are often overlooked while considering differential diagnoses in patients with musculoskeletal symptoms. The hindrance to mobility and the musculoskeletal discomfort owing to these myopathies are important causes of disability and depreciated quality of life in these patients. Endocrine myopathies occur due to the effects of endogenous or iatrogenic hormonal imbalance on skeletal muscle protein and glucose metabolism, disrupting the excitation-contraction coupling. Abnormalities of the pituitary, thyroid, parathyroid, adrenal, and gonadal hormones have all been associated with myopathies and musculoskeletal symptoms. Endocrine myopathies can either be the complication of a secondary endocrine disorder or a presenting symptom of a missed underlying disorder. Therefore, an underlying endocrine abnormality must always be excluded in all patients with musculoskeletal symptoms. This review presents a compilation of various endocrine myopathies, their etiopathogenesis, clinical presentation, diagnostic modalities, and treatment protocols.

Dropped head syndrome due to neuromuscular disorders: Clinical manifestation and evaluation

In this article, we discuss the clinical approach to patients with dropped head syndrome and identify the various neuromuscular causes of dropped head syndrome including muscle, neuromuscular junction, peripheral nerve and motor neuron etiologies. We aim to increase awareness of recognition the entity of dropped head syndrome and factors that may predict response to immunomodulating therapy in dropped head syndrome.

Fibromyalgia in a Patient with Cushing's Disease Accompanied by Central Hypothyroidism

A 39-year-old woman with a 3-year history of a rounded face developed widespread myalgia. Detailed examinations revealed no disorders that could explain the pain other than concomitant Cushing's disease and central hypothyroidism. Both the hypercortisolemia and hypothyroidism completely resolved after the patient underwent surgery to treat Cushing's disease, but she continued to experience unresolved myalgia and met the diagnostic criteria for fibromyalgia. Few studies have so far investigated patients with fibromyalgia associated with Cushing's syndrome. In our case, the hypothyroidism caused by Cushing's disease probably played an important role in triggering and exacerbating fibromyalgia. This highlights the need to examine the endocrine function in patients with muscle pain.

Thyroid disease and the nervous system

Thyroid disorders are common in the general population and in hospitalized patients. Thyroid disease may present first with neurological complications or else may occur concurrently in patients suffering other neurological disorders, particularly those with an autoimmune etiology. For this reason neurologists will commonly encounter patients with thyroid disease. This chapter provides an overview of the neurological complications and associations of disorders of the thyroid gland. Particular emphasis is placed on conditions such as thyrotoxic periodic paralysis and myxedema coma in which the underlying thyroid disorder may be occult leading to a first, often emergency, presentation to a neurologist. Information about clinical features, diagnosis, pathogenesis, therapy, and prognosis is provided. Emphasis is placed on those aspects most likely to be relevant to the practicing neurologist and the interested reader is directed to references to good, recent review articles for further information.

Vitamin E management of oxidative damage-linked dysfunctions of hyperthyroid tissues

INTRODUCTION

Thyroid hormones affect growth, development, and metabolism of vertebrates, and are considered the major regulators of their homeostasis. On the other hand, elevated circulating levels of thyroid hormones are associated with modifications in the whole organism (weight loss and increased metabolism and temperature) and in several body regions. Indeed, tachycardia, atrial arrhythmias, heart failure, muscle weakness and wasting, bone mass loss, and hepatobiliary complications are commonly found in hyperthyroid animals and humans.

RESULTS

Most thyroid hormone actions result from influences on transcription of T3-responsive genes, which are mediated through nuclear receptors. However, there is significant evidence that tissue oxidative stress underlies some dysfunctions produced by hyperthyroidism.

DISCUSSION

During the last decades, increasing interest has been turned to the use of antioxidants as therapeutic agents in various diseases and pathophysiological disorders believed to be mediated by oxidative stress. In particular, because elevated circulating levels of thyroid hormones are associated with tissue oxidative injury, more attention has been paid to explore the application of antioxidants as therapeutic agents in thyroid related disorders.

CONCLUSIONS

At present, vitamin E is among the most commonly consumed dietary supplements due to the belief that it, as an antioxidant, may attenuate morbidity and mortality. This is due to the results of numerous scientific studies, which demonstrate that vitamin E has a primary function to destroy peroxyl radicals, thus protecting polyunsaturated fatty acids biological membranes from oxidative damage. However, results are also available indicating that protective vitamin E effects against oxidative damage can be obtained even through different mechanisms.

Primary lung carcinoid, a rare cause of paraparesis: report of a case and review of the literature

Carcinoids are neuroendocrine tumors mainly involving the gastrointestinal tract, lungs and bronchi. They were considered benign with slow growth, but they can be malignant in a substantial percentage of patients (metastasizing to liver, bones, skin, etc). Endocrine activity results in carcinoid syndrome. Proximal myopathy has been reported in 7% of patients with carcinoid syndrome. Bronchopulmonary and thymic carcinoids producing adrenocorticotropic hormone can cause Cushing's syndrome, a main feature of which is myopathy. There are a few reports of carcinoids associated with paraneoplastic neurological syndromes, including neuropathy. We hereby present an extremely rare case of a primary lung carcinoid presented with paraparesis due to polyneuropathy, and review the relevant literature. To the best of our knowledge there is no similar previous report. Complete resolution of paraparesis after excision of the lung carcinoid suggests paraneoplastic neurological syndrome.

An unusual presenting symptom of graves' disease: myalgia

A 50-year-old female patient presented with severe myalgia involving her proximal muscles for 3-4 weeks. She also reported mild thyrotoxic symptoms over the same time period. Examination revealed mild thyrotoxicosis, a moderate diffuse goiter and no eye signs. The clinical picture was dominated by muscle pain and tenderness involving mainly her proximal arms and legs, her calves and her fingers, requiring opiate analgesia. Muscle power and tendon reflexes were normal. Laboratory evaluation revealed undetectable serum thyroid stimulating hormone (TSH) with raised FT4, FT3 and positive TSH receptor antibodies. Treatment with carbimazole was started. Additional laboratory investigations were negative (inflammatory markers, creatine kinase and antibodies to antinuclear antibodies, gastric parietal cell, smooth muscle, mitochondrial, dsDNA, centromere, extractable nuclear antigen (ENA) ribonucleoprotein, ENA Sm, ENA Ro, ENA Anti-La, ENA Scl70, ENA Jo-1, anti-CCP and rheumatoid factor). Further assessment in the rheumatology clinic confirmed there was no small joint tenderness or loss of range of movement of her limbs, but widespread and profound muscle tenderness of the common extensors of the forearms, biceps, trapezius, calves and thighs. She was treated symptomatically with analgesic medication and continued on carbimazole. A month later she was euthyroid and her myalgia had resolved. Hyperthyroidism has a profound effect on skeletal muscle and often leads to myopathy. Severe myalgia in association with Graves' disease is rare and resolves with the restoration of euthyroidism.

[Congenital and endogenous endocrine myopathy]

Disorders in endocrinological pathways rarely lead to manifest acquired or endogenous myopathy so that an interdisciplinary evaluation between neurology and endocrinology is essential for these disorders. Asymptomatic or forme fruste variants may be more common and even underdiagnosed in these circumstances. Dysbalance disorders of protein synthesis, electrolytes and carbohydrates can lead to several rare forms of myopathy due to the dependence on hormonal metabolism. In general, the main neuromuscular symptom is proximal weakness, sometimes in addition to myalgia and muscle atrophy. Endocrine myopathies are usually reversible by treatment of the underlying disease. The severity of the endocrinopathy is of fundamental importance for the long-term clinical outcome.

Dropped head syndrome: diagnosis and management

Dropped head syndrome (DHS) is a relatively rare condition, with a broad differential diagnosis. This deformity has significant implications on the health and quality of life of affected individuals. While surgery seems to be an obvious therapeutic option, there is a paucity of information on surgical intervention with no clear consensus on an optimal approach or timing. We present a case of DHS in a young woman to illustrate this condition, and review the current literature. Although at present the only definitive solution for correction and stabilization of DHS is surgical intervention involving multilevel instrumented fixation and fusion, this condition requires a persistent medical workup and treatment of reversible causes before surgical intervention is contemplated.

A case of Sheehan's syndrome that manifested as bilateral ptosis

Hypothyroidism can cause a variety of signs and symptoms of the neuromuscular system. However, ptosis in a patient with hypothyroidism is very rare. We report here on a case of central hypothyroidism that was due to Sheehan's syndrome and it manifested as bilateral ptosis in a 51-yr-old woman. She complained of exertional dyspnea and weakness. About 25-yr ago, she had a history of severe postpartum vaginal bleeding. The laboratory studies demonstrated hypopituitarism with secondary hypothyroidism. The ptosis was improved by replacement of thyroid hormone. Hypothyroidism should be considered in the differential diagnosis of patients who manifest with ptosis and that prompt replacement of hormone can lead to a complete recovery.

Painful hypoadrenalism

A 61-year-old man presented with diffuse myalgia and arthralgia. The physical examination showed diffuse musculoskeletal tenderness and joint stiffness without the presence of synovitis or arthritis. Nerve conduction study showed combined mild axonal degenerative and demyelinating change. Muscle biopsy analysis showed unspecific mild muscle atrophy with myopathic changes found on electromyography. A diagnosis of isolated adrenocorticotropic hormone deficiency was made on the basis of endocrinological evaluation. The widespread musculoskeletal pain resolved as a result of administration of physiological dose of hydrocortisone replacement. In a patient with unexplained rheumatic symptoms, adrenocortical insufficiency should be considered in the possible aetiology.

The pituitary-adrenal axis and body composition

The activity of the pituitary-adrenal axis can profoundly impact on body composition. This is dramatically seen in Cushing's syndrome (CS) but changes in body composition are also implicated in depression and alcoholic pseudocushing's. The pathophysiological mechanisms underlying these changes remain poorly understood. Changes to body composition in CS include increased fat mass, decreased bone mass, thinning of the skin and reduced lean mass. Why these tissues are affected so dramatically is unclear. Additionally, the change in body composition between individuals varies considerably for reasons which are only now becoming evident. This paper reviews the phenotypic changes with altered pituitary-adrenal axis activity and discusses the mechanisms involved. The primary focus is on adipose, bone, muscle and skin since the most dramatic changes are seen in these tissues.

Polymyositis-like syndrome caused by hypothyroidism, presenting as camptocormia

Polymyositis-like syndrome characterized by proximal muscle weakness and elevation of muscle enzymes may be a presenting manifestation of hypothyroidism. Camptocormia, which can be caused by myopathy of the paraspinal muscles, is an involuntary truncal flexion of the thoracolumbar spine while standing or walking. Among various neuromuscular disorders, hypothyroidism has not been reported in the literature as a cause of camptocormia. This is the first report of polymyositis-like syndrome with camptocormia caused by hypothyroidism.

Hypothyroid myopathy with manifestations of Hoffman's syndrome and myasthenia gravis

Although hypothyroid myopathy is seen frequently and the relationship with autoimmune hypothyroidism and myasthenia gravis is well known, specific forms of hypothyroid myopathy such as Hoffman's syndrome (HS) are rarely described. Here we describe a 40-year-old patient with Hashimoto thyroiditis showing symptoms and signs of two discrete forms of hypothyroid myopathy (HS and myasthenic syndrome) together. To our knowledge this is the first reported case with features of both of these syndromes. We discuss the diagnosis, speculate whether this patient may represent a unique form of hypothyroid myopathy, and report the 6-month follow-up of the patient both clinically and electrophysiologically.

Testosterone deficiency myopathy

Testosterone is recognized to have a positive effect on nitrogen balance and muscle development in hypogonadal men, but significantly myopathy secondary to testosterone deficiency has been reported only rarely. We describe a patient who presented with a myopathy associated with testosterone deficiency, and who demonstrated a significant functional and myometric response to treatment.

Muscle function in patients with primary hyperparathyroidism

The muscle contraction of the anterior tibial muscle was investigated by measurements of electrically stimulated and computer-analyzed muscle twitches in 18 unselected patients with primary hyperparathyroidism (HPT) and in 20 healthy control persons. The HPT patients had a lower muscle twitch tension (TT) at single stimulation, compared with the control group [76 +/- 24 N (SD) and 99 +/- 33 N respectively, P less than 0.05]. At high-frequency stimulation the difference in muscle force increased, and at 20 Hz stimulation the force in the HPT patients was 73% of that in the controls (P less than 0.01). There were no differences between the HPT patients and the control persons in neither contraction time nor half relaxation time at single muscle twitch nor in twitch potentiation after 20 and 90 seconds maximal voluntary contraction. The results indicate that patients with primary HPT have an impaired muscle function of probable importance for their symptoms of weakness and generalized fatigue.

Sleep apnea and hypothyroidism: mechanisms and management

PURPOSE

There is a high incidence of sleep apnea in patients with untreated hypothyroidism. Thyroxine treatment is said to significantly reduce the apnea index and length and sleep apnea symptoms. We undertook a review of 10 consecutive hypothyroid patients with sleep apnea to investigate mechanisms and management of these two disorders.

PATIENTS AND METHODS

Polysomnograms were obtained in 10 consecutive hypothyroid patients referred to our sleep disorders unit. All patients were studied while hypothyroid. Eight patients were restudied later when euthyroid. Lung function, blood gas values, and awake supraglottic resistance were also assessed in each patient.

RESULTS

All 10 patients had sleep apnea and were treated with thyroxine. In one patient, hypothyroid myopathy involving the upper airway was demonstrated to be a potential mechanism of sleep apnea in hypothyroidism. Nocturnal angina and ventricular arrhythmias developed in two patients, despite the use of low thyroxine doses. Nasal continuous positive airways pressure (CPAP) was begun in eight patients. Initiation of CPAP prevented further angina or arrythmia in the patients with these cardiac complications. Six of the eight patients who were available for follow-up studies had persistent sleep apnea despite an euthyroid status (apnea index before thyroxine, 51 +/- 6; apnea index after thyroxine, 45 +/- 8), and CPAP therapy was continued in these patients.

CONCLUSION

Our experience suggests that the apnea index does not decrease significantly in all patients with hypothyroidism and sleep apnea when euthyroidism is achieved. Treatment of hypothyroidism in the presence of sleep apnea is potentially hazardous and may lead to cardiovascular complications. Management by a combination of CPAP and low-dose thyroxine is helpful in this situation.

Maximal isokinetic muscle strength in patients with primary hyperparathyroidism before and after parathyroid surgery

Primary hyperparathyroidism (HPT) is associated with symptoms of generalized fatigue and muscle weakness. The purpose of this study was to investigate muscular function in HPT quantitatively and to evaluate the effect of parathyroid surgery in this respect. The maximal isokinetic muscle strength (peak torque) of knee extension and flexion was measured with a Cybex-II dynamometer in 16 patients with primary HPT (mean serum calcium 2.81 +/- 0.14 mmol/l), four of whom had subjective impairment of strength, and in nine control patients submitted to hemithyroidectomy due to atoxic thyroid adenoma. Before surgery there was no significant difference in muscle strength between the two groups, neither was there any consistent relationship between the subjective feeling of muscular weakness and the measured peak torque. Seven months after surgery the HPT patients had increased their muscle strength by 8 per cent (P less than 0.05). The improvement was correlated with the pre-operative serum calcium levels (r = 0.56, P = 0.02) and was particularly seen in patients with pre-operative subjective muscular weakness. Patients with only slightly raised calcium values and without subjective muscular symptoms did not benefit clearly from surgery, compared with the controls. The study demonstrates that HPT patients, especially those with neuromuscular symptoms, can improve their muscle strength after parathyroid surgery.

Muscle disease--a primer

True weakness, especially in the proximal muscles, is a symptom of muscle disease. In differential diagnosis, conditions mimicking myopathy can be excluded on the basis of physical findings, various tests, and when appropriate, muscle biopsy. Once myopathy has been diagnosed, the physician needs to determine whether the cause is toxic, endocrine, inflammatory, metabolic, dystrophic, or congenital. The distinguishing features of these categories help in reaching a specific diagnosis. Because most of the common myopathies can be treated, recognition is important.

Myopathy in Addison's disease

Since the first description of primary adrenocortical insufficiency by Thomas Addison in 1855 several large series of patients with Addison's disease have been published. The common signs and symptoms include: weakness, hyperpigmentation, weight loss, gastrointestinal complaints, and hypotension. It is rare for patients with Addison's disease to present with musculoskeletal symptoms including flexion contractures, hyperkalaemic neuromyopathy, Guillain-Barré syndrome, migratory myalgia, sciatica-like pain, and low back pain. Myopathy has not been previously described in Addison's disease. Herein we report a patient presenting with severe hyponatraemia and myopathy which resolved after steroid replacement therapy.

Muscle dysfunction in male hypogonadism

Twenty-eight consecutive male patients with primary and secondary hypogonadism (14 each) were evaluated clinically and electrophysiologically for muscle dysfunction. Although generalised muscle weakness was initially reported by only 9 patients, on direct questioning, it was recorded in 19. Objective weakness was found in 13 patients and it involved both the proximal and distal limb muscles. Quantitative electromyography showed evidence of myopathy in the proximal muscle in 25 patients, i.e., reduced MUP duration and amplitude with increased polyphasia in the deltoid and the gluteus maximus. There were no denervation potentials. None of the patients showed clinical neuropathy or NCV abnormalities. Thus, the profile of muscle involvement in hypogonadism closely simulates limb-girdle muscular dystrophy and other endocrine myopathies. The incidence of muscle involvement was higher in secondary hypogonadism. Diminished androgens in primary hypogonadism and diminished growth hormone in the secondary hypogonadism are probably responsible for the myopathy.

Gonadotropin, prolactin and TSH secretion in patients with myasthenia gravis

Hypothalamic pituitary function was studied in 13 patients with myasthenia gravis. Gonadotropin, TSH, and prolactin dynamics were investigated using conventional provocative stimuli. No consistent abnormality was found in either gonadotropin or prolactin release. Abnormal TSH responses to TRH administration was present in six of the 13 patients in association with normal free thyroxine indices and the absence of antithyroid antibodies. This latter observation is relevant when the association of myasthenia gravis with hyperthyroidism, thyroiditis and hypothyroidism is considered.