Causes of Hypothyroidism

Causes of HypothyroidismINTRODUCTIONHypothyroidism is the intimately common prevailing ductless gland disorder among all endocrine gland maladies. It is an altered metabolic state, when the body produces low amount of thyroid hormone. Hypothyroidism is non only a disorder of endocrine system, it also affects almost all the organ system of our body. It shows a full(a) range of disease severity from asymptomatic state to coma and do it an elusive clinical entity9 . thyroid hormone in addition to administration the rate of metabolism of fats, carbohydrates and proteins, it also regulates the timing and pace of the CNS development. It is extremely Copernican for the growth of cerebral , cerebellar cortex, axonal proliferation, branching of dendrites, synaptogenesis, and myelination . Thyroid hormone enhances the wakefulness, response to various stimuli wish well auditive sensation, learning and repositing capacity1. By enhancing the gene expression it influences the synthesis of myelin. Myelin synthesis is an important factor determining the speed of impulse transmission along the composite plant neural pathway which mediates the evoked potential3 .Sometimes hypothyroidism is referred to as Silent unsoundness because the early stage of disease it is asymptomatic. About 1.6 billion people be at risk of getting thyroid disorders worldwide4. According to NHANES III near 4 5% of population in the developed world is poor from hypothyroidism and more or less 4 15% of people by subclinical hypothyroidism5 .In a developing country like India, unity deficiency is the most common cause of hypothyroidism. In India, hypothyroidism is classified under the group of iodin Deficient Disorder (IDD) 6. Since 1983 India has been following the Universal Salt Iodization Programme. As a result of it, there has been a decline in the prevalence of IDD 7. In 2004, WHO assessment of global iodine status documented that India has optimal iodine nutrition and now India i s undergoing transition from iodine deficiency to sufficiency phase8 . exclusively a nationwide comprehensive epidemiological study done in the eight cities of India found that the prevalence of hypothyroidism was 10.95%. One third of them (3.47%) are non hitherto aware of their disease. Subclinical Hypothyroidism was observed in 8.02% of people. Females are more prone to have hypothyroidism than males (15.86% to 5.02%). Unnikrishnan AG et al has also observed last prevalence of hypothyroidism among the Indian adult population6 .The well-known symptoms and signs of hypothyroidism are dry skin, free weight gain, cold intolerance, muscle cramps, hoarseness of voice and constipation10 . As thyroid hormone is essential for the spooky system maturation , central and peripheral nervous system disfunctions are also important consequences of hypothyroidism. About 60 90% of the patients may have features of peripheral nervous system dysfunction like weakness, paraesthesia and postura l imbalance . The CNS manifestations of hypothyroidism seen in 60 to 80% of patients which include delayed mentation, sensory deficits, depression11 . It also produces delay in the neuronic conduction velocity, alterations in earshot threshold and sensation of smell . on the whole these neurological complications of hypothyroidism will resolve completely with thyroid hormone transposition especially when diagnosed at the early stage12.The peripheral nervous system dysfunction has been studied in hypothyroid patients by a variety of techniques. But the studies in favor of quantification of CNS dysfunction were very sparse. The CNS pastime in hypothyroid patients can be identified with the help of existing advanced electrophysiological studies. Among the electrophysiological studies evoked potentials provide a more reliable and objective measure of the operative integrity of the related sensory pathway13 . Among the various evoked potentials essays, brain stem elicited Response Audiometry (BERA) has been emerged as an effective method of revealing the involvement of auditory pathway even in asymptomatic stage itself11 .Brainstem Evoked Auditory Response are produced in response to shortened auditory stimulation14,15 . In this technique following a brief acoustic stimulus, a series of potentials are generated which corresponds to the sequential activation of peripheral, pontomedullary, pontine and midbrain service of auditory pathway. So BERA helps to evaluate the integrity of the auditory pathway13 . Persons who are having brachydactylic brainstem response to auditory stimuli more prone to develop sensorineural Hearing pass16 .In 1948 Means states that Hearing loss is one of the troublesome symptom of hypothyroidism and it may be conductive, sensorineural or mixed listening loss. About 25 to 30% of the hypothyroid patients having loss, but the exact incidence not yet known. So many researchers did study to find the type of auditory sense loss in hy pothyroid patients. Howarth and Lloyd proposed that perceptive deafness is the type of hearing loss in hypothyroidism. (9) Rau et al, Bhatia et al, Vont Hoff and Stuart , Parving et al and Isam et al were also accepted that sensorineural hearing loss was the predominant type of hearing loss in hypothyroidism people. Malik et al said that the site of lesion in auditory pathway trunk speculative , may be at several levels viz in the centerfield ear, at cochlea and retrocochlear sites 17. The integrity of the auditory pathway is essential for the capture of the acoustic signal by the external ear to the coding of signals in the auditory cortex13 .Hearing loss is an invisible abnormality which will lead to so many devastating consequences in interpersonal communication, psychosocial wellbeing, quality of life and frugal independence. Hearing loss in infants and children due to congenital hypothyroidism results in sober impairment in language, communication skills, cognitive and emot ional development. In adults hearing loss will lead to loneliness, social isolation, psychiatric disturbances, depression, occupational tenor and relatively low earnings18. There are literatures pointing out that early treatment of hypothyroidism will reverse the hearing loss 19-22.Electrophysiological testing for finding the practicable integrity of auditory pathway is rarely performed in hypothyroid patients in neurology and otolaryngology practice. Now a days BAER is mainly used for application the preterm infants and also prior to cochlear implantation. But it was proved that the delay in the auditory processing time may provide the information about the subclinical involvement of central as well as peripheral neuropathy in hypothyroid individuals 8. So they can be used to assess both(prenominal) normal and abnormal auditory function in the field of research. So that BERA can be used as a screening test to find the CNS involvement and the hearing loss in hypothyroid patien ts even in the earlier stage itself.In this study an endeavor has been make to find the changes in the brainstem auditory evoked responses in impudently diagnosed hypothyroid individuals.