Introduction
Hypothyroidism is the most common prevailing endocrinal upset among all endocrinal maladies. It is an altered metabolic province, when the organic structure produces deficient sum of thyroid endocrine. Hypothyroidism is non merely a upset of hormone system, it besides affects about all the organ system of our organic structure. It shows a broad scope of disease badness from symptomless province to coma and made it an elusive clinical entity9.
Thyroid endocrine in add-on to regulating the rate of metamorphosis of fats, saccharides and proteins, it besides regulates the timing and gait of the CNS development. It is highly of import for the growing of intellectual, cerebellar cerebral mantle, axonal proliferation, ramification of dendrites, synaptogenesis, and myelination. Thyroid endocrine enhances the wakefulness, response to assorted stimulations like audile esthesis, larning and memory capacity1. By heightening the cistron look it influences the synthesis of medulla. Myelin synthesis is an of import factor finding the velocity of impulse transmittal along the complex nervous tract which mediates the elicited potency3.
Sometimes hypothyroidism is referred to as “Silent Disease” because the early phase of disease it is symptomless. About 1.6 billion people are at hazard of acquiring thyroid upsets worldwide4. Harmonizing to NHANES III about 4 – 5 % of population in the developed universe is enduring from hypothyroidism and about 4 – 15 % of people by subclinical hypothyroidism5.
In a underdeveloped state like India, iodine lack is the most common cause of hypothyroidism. In India, hypothyroidism is classified under the group of Iodine Deficient Disorder ( IDD )6. Since 1983 India has been following the Universal Salt Iodization Programme. As a consequence of it, there has been a diminution in the prevalence of IDD7. In 2004, WHO appraisal of planetary I position documented that India has optimum iodine nutrition and now India is undergoing passage from iodine lack to sufficiency stage8. But a countrywide comprehensive epidemiological survey done in the eight metropoliss of India found that the prevalence of hypothyroidism was 10.95 % . One tierce of them ( 3.47 % ) are non even cognizant of their disease. Subclinical Hypothyroidism was observed in 8.02 % of people. Females are more prone to hold hypothyroidism than males ( 15.86 % to 5.02 % ) . Unnikrishnan AG et Al has besides observed high prevalence of hypothyroidism among the Indian grownup population6.
The well-known symptoms and marks of hypothyroidism are dry tegument, weight addition, cold intolerance, musculus spasms, gruffness of voice and irregularity10. As thyroid endocrine is indispensable for the nervous system ripening, cardinal and peripheral nervous system disfunctions are besides of import effects of hypothyroidism. About 60 – 90 % of the patients may hold characteristics of peripheral nervous system disfunction like failing, paresthesia and postural instability. The CNS manifestations of hypothyroidism seen in 60 to 80 % of patients which include delayed thinking, centripetal shortages, depression11. It besides produces hold in the neural conductivity speed, changes in hearing threshold and esthesis of odor. All these neurological complications of hypothyroidism will decide wholly with thyroid endocrine replacing particularly when diagnosed at the early phase12.
The peripheral nervous system disfunction has been studied in hypothyroid patients by a assortment of techniques. But the surveies in favour of quantification of CNS disfunction were really thin. The CNS engagement in hypothyroid patients can be identified with the aid of bing advanced electrophysiological surveies. Among the electrophysiological surveies evoked potencies provide a more dependable and nonsubjective step of the functional unity of the related sensory tract13. Among the assorted elicited potencies trials, Brainstem Evoked Response Audiometry ( BERA ) has been emerged as an effectual method of uncovering the engagement of audile tract even in symptomless phase itself11.
Brainstem Evoked Auditory Response are produced in response to brief audile stimulation14,15. In this technique following a brief acoustic stimulation, a series of potencies are generated which corresponds to the consecutive activation of peripheral, pontomedullary, pontine and midbrain part of audile tract. So BERA helps to measure the unity of the auditory tract13. Persons who are holding unnatural brain-stem response to auditory stimulations more prone to develop Sensorineural Hearing loss16.
In 1948 Means provinces that Hearing loss is one of the troublesome symptom of hypothyroidism and it may be conductive, sensorineural or assorted hearing loss. About 25 to 30 % of the hypothyroid patients holding loss, but the exact incidence non yet known. So many research workers did analyze to happen the type of hearing loss in hypothyroid patients. Howarth and Lloyd proposed that perceptive hearing loss is the type of hearing loss in hypothyroidism. ( 9 ) Rau et Al, Bhatia et Al, Von’t Hoff and Stuart, Parving et Al and Isam et Al were besides accepted that sensorineural hearing loss was the prevailing type of hearing loss in hypothyroidism people. Malik et Al said that the site of lesion in audile tract remains bad, may be at several degrees viz in the in-between ear, at cochlea and retrocochlear sites17. The unity of the audile tract is indispensable for the gaining control of the acoustic signal by the external ear to the cryptography of signals in the auditory cerebral mantle13.
Hearing loss is an unseeable abnormalcy which will take to so many lay waste toing effects in interpersonal communicating, psychosocial well-being, quality of life and economic independency. Hearing loss in babies and kids due to inborn hypothyroidism consequences in serious damage in linguistic communication, communicating accomplishments, cognitive and emotional development. In grownups hearing loss will take to loneliness, societal isolation, psychiatric perturbations, depression, occupational emphasis and comparatively low net incomes18. There are literatures indicating out that early intervention of hypothyroidism will change by reversal the hearing loss19-22.
Electrophysiological testing for happening the functional unity of audile tract is seldom performed in hypothyroid patients in neurology and rhinolaryngology pattern. Now a yearss BAER is chiefly used for testing the preterm babies and besides prior to cochlear nidation. But it was proved that the hold in the auditory processing clip may supply the information about the subclinical engagement of cardinal every bit good as peripheral neuropathy in hypothyroid persons8. So they can be used to measure both normal and unnatural auditory map in the field of research. So that BERA can be used as a testing trial to happen the CNS engagement and the hearing loss in hypothyroid patients even in the earlier phase itself.
In this survey an enterprise has been made to happen the alterations in the brain-stem auditory elicited responses in freshly diagnosed hypothyroid persons.