|Year : 2016 | Volume
| Issue : 3 | Page : 131-135
Nerve conduction studies in patients with primary hypothyroidism
Sampada Swapneel Karne, Nilima Sudhakar Bhalerao
Department of Medicine, Smt. Kashibai Navale Medical College, Pune, Maharashtra, India
|Date of Web Publication||27-Oct-2016|
Sampada Swapneel Karne
E 404, Tain Square, Opposite Inamdar Hospital, Fatimanagar, Pune - 411 013, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: Hypothyroidism is an important cause of peripheral as well as focal neuropathy. Reported prevalence of neuropathy in hypothyroidism is varied widely. Objective: To study nerve conduction abnormalities and to correlate electrodiagnostic findings with clinical features in patients with primary hypothyroidism. Materials and Methods: This study was done in Smt. Kashibai Navale Medical College, Pune, Maharashtra. Adult patients with primary hypothyroidism were included. Patients with other possible causes of neuropathy were excluded. Detailed medical history was obtained, and clinical examination and nerve conduction study by electrophysiological method were done in all patients. Results: Total 40 patients were included, of which, 25% patients showed evidence of neuropathy. Six patients had carpal tunnel syndrome while four had other peripheral neuropathy. Presence of neuropathy correlated independently with advanced age and female gender. There was significant correlation between presence of signs and symptoms of neuropathy to electrophysiologically confirmed neuropathy. Occurrence of neuropathy was more common in patients with duration of disease more than 5 years (44.44%) and obesity (50%), but these findings were not statistically significant (P = 0.08 and 0.09, respectively). No correlation found between etiology of disease, serum thyroid-stimulating hormone level and occurrence of neuropathy (P = 0.43, 0.9, respectively). Conclusion: Advanced age and female gender are important risk factors for development of neuropathy in patients with hypothyroidism. The thorough clinical examination is very important as clinical signs and symptoms are sensitive predictors for the presence of neuropathy.
Keywords: Hypothyroidism, nerve conduction study, neuropathy
|How to cite this article:|
Karne SS, Bhalerao NS. Nerve conduction studies in patients with primary hypothyroidism. Thyroid Res Pract 2016;13:131-5
| Introduction|| |
Nervous system gets affected in hypothyroidism in a variety of ways. Neuropathy is one of them. Screening of thyroid disease has become the routine part of general medicine care. This study was designed to study neuropathy in patients with hypothyroidism. The types of neuropathy seen in hypothyroidism include focal entrapment neuropathy and less common peripheral neuropathy. , Entrapment neuropathy-like carpel tunnel syndrome (CTS), which is a common occurrence in hypothyroidism, if diagnosed early can be effectively treated.
| Materials and methods|| |
The present study was approved by Ethics Committee of our institute, that is, Smt. Kashibai Navale Medical College and General Hospital, Pune, Maharashtra. Written informed consent was obtained from all the patients before enrolling them in the study.
Aims and objectives
To study nerve conduction abnormalities and to correlate electrodiagnostic findings with clinical features in patients with primary hypothyroidism.
The present, cross-sectional study was carried out in the Department of Medicine, Smt. Kashibai Navale Medical College, Pune, Maharashtra, from June 2013 for 1 year. All adult patients (age > 18 years), who consented to participate in the study, with diagnosis of primary hypothyroidism, irrespective of the etiology, attending outdoor patient department, or admitted in medicine wards were included in this study.
Patients with secondary hypothyroidism or with other possible causes of neuropathy (e.g., diabetes mellitus, alcoholism, liver or kidney diseases, use of drugs known to cause neuropathy, rheumatoid arthritis, malignancy, megaloblastic anemia, other serious illness or family history of neuropathy, etc.,) were excluded from this study.
The study objectives were explained to each patient, and written informed consent was obtained. Detailed medical history regarding duration of disease and medical treatment was taken. Duration of disease was defined as the period from the diagnosis to the date of enrollment in the study. The common features of nerve dysfunctions such as pain, cramps, paresthesia, and weakness were asked and documented in the data sheet. The complete medical examination was carried out for every patient. Body mass index (BMI) was calculated for each patient. Patient with BMI more than or equal to 25 kg/m 2 and more than or equal to 30 kg/m 2 was considered as overweight and obese, respectively.
The biochemical profile was evaluated to confirm the diagnosis of primary hypothyroidism. Thyroid function tests including serum T3, T4 or free T3, free T4, and thyroid stimulating hormone (TSH) were measured. Moreover, nerve conduction studies (NCSs) were done by electrophysiological method. The NCS was performed at room temperature, with normal body temperature, on two channel electromyography (EMG) machine by Recorders and Medicare Systems, Chandigarh. Motor and sensory nerve conductions including F responses were recorded. Median and ulnar nerves of the upper limb and peroneal, tibial and sural nerves of the lower limb were tested. Latency, amplitude, and conduction velocity were noted and compared with age-specific reference data of our electrophysiology laboratory.
The statistical tests used were Chi-square test for association of various factors with respect to nerve conduction test interpretation; unpaired t-test for calculating mean latency, amplitude, and conduction velocity of various nerves with respect to various factors under consideration; z-test for calculating the confidence interval of latency, amplitude, and conduction velocity of various nerves; and Kruskal-Walis test in case of nonhomogeneous samples. P < 0.05 was considered to be statistically significant. Epi Info™ version 22.214.171.124, which is a statistical software for epidemiology developed by Centers for Disease Control and Prevention (CDC) was used for statistical analysis using operating system support windows 7.
| Results|| |
Summary of patients' baseline characteristics is described in [Table 1]. A total of 40 patients who met the diagnostic criteria of primary hypothyroidism and inclusion criteria were included in this study. The sample comprised 34 females (85%) and 6 males (15%) with age group ranging from 20 years to 75 years. In 9 (22.5%) patients, thyroid peroxidase antibodies were positive, 4 (10%) patients were postradiation therapy, and 27 (67.5%) were idiopathic. Duration of disease was <1 year in 16 patients (40%), 1-5 years in 15 patients (37.5%), and more than 5 years in 9 patients (22.5%). Fourteen patients (35%) had normal BMI, 16 (40%) were overweight, and 10 (15%) were obese. Thirty patients (75%) were on hormonal replacement therapy for hypothyroidism at the time of inclusion in the study, while 10 patients (25%) who were newly diagnosed were not on any treatment.
Eleven patients (27.5%) documented symptoms suggestive of neuropathy most common being paresthesia. Abnormal neurological examination suggestive of neuropathy was present in 12 (30%) patients; the most common was the impairment of the deep tendon reflexes. In none patients, signs of muscle atrophy or hypotonia were seen. Presence of either signs or symptoms suggestive of presence of neuropathy was seen in 20 patients (50%). Of these 20 patients, NCS confirmed the presence of neuropathy in 8 patients (P = 0.03).
TSH bioassay was done in all cases; while TT3 and TT4 in 24 cases, and FT3 and FT4 in 16 cases. With reference to standard limits, TSH was normal in 10 cases (25%), and abnormal in 30 (75%) with mean 48.65 IU/L. In patients with normal NCS, mean value of serum TSH was 36.38; whereas, in patients with abnormal, NCS it was 39.73.
By electrophysiological study, occurrence of neuropathy was found in 10 patients (25%). The mean of amplitude, conduction velocity, and latency of individual motor and sensory nerves, that is, median, ulnar, tibial, peroneal, sural nerve, in patients with normal NCS, are shown in [Table 2]. Six patients had CTS; of which, 4 patients had bilateral, and 2 patients had unilateral CTS. Four patients showed peripheral neuropathy. One patient had right sural neuropathy. Other had pure sensory neuropathy affecting right median and ulnar nerves. The third patient had pure motor mononeuropathy affecting left median while the fourth had sensory motor neuropathy affecting lower limb with right peroneal and sural neuropathy [Table 3].
|Table 2: Electrophysiological properties in patients with normal NCS (n=30) |
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Presence of neuropathy correlated independently with advanced age and female gender. In 13 patients with age >45 years, 4 had abnormal NCS (30.7%, P = 0.03), and of 34 female patients, 9 had neuropathy (26.4%, P = 0.000). Occurrence of neuropathy was more common in patients with duration of disease more than 5 years (44.44%) and obesity (50%), but these findings were not statistically significant (P = 0.08 and 0.09, respectively). No correlation found between etiology of disease, serum TSH level and occurrence of neuropathy (P = 0.43, 0.9, respectively) [Table 4].
| Discussion|| |
Polyneuropathy in hypothyroidism has been described in many studies. ,,, Mechanism of development of neuropathy in hypothyroidism is not well-understood. Metabolic alterations induced by hypothyroidism are responsible for peripheral neuropathy.  Adenosine triphosphate (ATP) deficiency and reduced ATPase activity with decreased N + /K + pump activity cause alteration in axonal transport leading to peripheral neuropathy. These changes initially damage function in the nerve, and later induce structural alterations.  There are studies which reported primary axonal degeneration while some reported demyelination as the predominant feature of neuropathy in hypothyroidism. ,, Median nerve entrapment at the wrist due to deposition of mucinous material in the tissue surrounding the nerve is most frequent cause of nerve damage in hypothyroidism. Reported prevalence of neuropathy in hypothyroidism is varied widely. Beghi et al. reported 72% patients with polyneuropathy, commonly affecting sural nerve followed by median sensory.  While Eslamian et al. described 15% case with neuropathy,  Ajeena reported high prevalence of sensory neuropathy (44%), followed by sural mononeuropathy (43%) and CTS (39.6%).  In most of the studies, reported neuropathies in hypothyroidism were mild and mainly sensory type , and even reported in clinically euthyroid patients.  In our study population, we had 25% (n = 10) patients with primary hypothyroidism with abnormal electrophysiological findings. Most common occurrence was CTS (n = 6), then sensory (n = 2), sensory-motor (n = 1), and pure motor (n = 1). Schwartz et al. discussed that the presence of tarsal tunnel syndrome (TTS) as a common finding in myxedema patients but less frequent than CTS.  None of the patients in our study population had TTS.
The finding in the present study, that neuropathy increases as age advances supports other population-based studies. One study estimated that the prevalence of peripheral neuropathy in the family medicine setting is 8% in persons 55 years and older.  In the present study, female gender significantly correlated with presence of neuropathy. Eslamian et al., in a study of 40 untreated patients with primary hypothyroidism found no significant correlation between female gender and occurrence of neuropathy or myopathy; however, he found significant relation of female gender to the presence of CTS.  Occurrence of neuropathy is related to duration of disease possibly due to long-term accumulation of mucinous tissue.  This is also supported by Nemni et al.  This might suggest that the metabolic changes in hypothyroidism, causing electrophysiological changes may occur early in the course of the disease. 
A high BMI is a well-recognized risk factor for neuropathy in diabetic as well as nondiabetic individuals, due to metabolic alteration.  Though not statistically significant, we also found the same correlation between high BMI and neuropathy in hypothyroidism. Careful clinical examination is very important. It is sensitive predictor (sensitivity 80%) for the presence of neuropathy. In this study population, we found significant correlation between presence of signs and/or symptoms of neuropathy to electrophysiologically confirmed neuropathy.
| Conclusion|| |
Advanced age and female gender are important risk factors for development of neuropathy in patients with hypothyroidism. The thorough clinical examination is very important as clinical signs and symptoms are sensitive predictors for the presence of neuropathy. The present study may be helpful in creating awareness of neuropathy in hypothyroidism among physicians and patients.
Major shortcomings of this study are the small number of patients and lack of age and sex-matched control group. Furthermore, we could not perform EMG in all patients.
We would like to thank Dr. S. Singru, Associate Professor in Community Medicine, for statistical analysis in this study project. We also gratefully acknowledge the contribution of Mrs. Kalavathi Reddy, Technician in EMG Department. We bear wholehearted gratefulness for the patients who participated in this study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]