Auditory Investigations in Hypothyroidism

Abstract

Twenty patients with thyroprivic hypothyroidism with a mean age of 34.8 years (range: 15-50 years) were investigated. Peripheral/central functions of the auditory system were assessed in the hypothyroid state and they were re-evaluated in the euthyroid state after treatment with levothyroxine. The mean observation period for re-evaluation was 3.7 months (range 3-7 months). Sixteen patients with hypothyroidism (80%) demonstrated hearing loss when compared with randomly selected age- and sex-matched normal subjects. Twelve of the hypothyroid patients had sensorineural hearing loss and 4 had mixed loss. Special hearing tests revealed a cochlear type of hearing loss. The tympanogram curve was of Type B in one ear of each of the 4 patients. Brainstem electric response audiometry showed prolonged, absolute latency of wave V and interpeak latencies I-III and I-V. The amplitudes of waves I, II and V were reduced. Following treatment with levothyroxine a statistically significant improvement in hearing thresholds was observed by pure-tone audiometry. Tympanogram curves returned to normal in 3 out of 4 patients. Brainstem electric response parameters did not show significant reversibility to normalcy following treatment. The results of auditory investigations suggest a causal relationship between hypothyroidism and hearing loss. The site of lesion in the auditory system is probably at several levels, viz. in the middle ear, and at cochlear and retrocochlear sites.

Alterações na audiometria de tronco encefálico em mulheres adultas com hipotireoidismo subclínico

“…A maioria dos trabalhos realizados em adultos com hipotireoidismo clínico submetidos a ABR resultaram em evidências de aumento de LA V e da LIP I-V. [19][20][21]23 Alguns também encontraram alargamento da LIP I-III. 19,20 Outros autores ainda acharam prolongamento da LIP III-V. 23 Aqui, vale a pena ressaltar que todos os pesquisadores acima mencionados enfocaram o hipotireoidismo clínico, enquanto que nós nos reportamos à forma subclínica da doença.…”

“…19,20 Outros autores ainda acharam prolongamento da LIP III-V. 23 Aqui, vale a pena ressaltar que todos os pesquisadores acima mencionados enfocaram o hipotireoidismo clínico, enquanto que nós nos reportamos à forma subclínica da doença. Ou seja, nossos resultados apontam para o fato de mesmo quando a insuficiência tireóidea ainda não atingiu seus estágios mais desenvolvidos, já poderá ocorrer distúrbio de condutibilidade nervosa auditiva central, caracterizado por atraso na propagação do estímulo.…”

“…17 A literatura nos revela vários trabalhos dedicados à investigação eletrofisiológica em pacientes com distúrbios tireoidianos e, em sua grande maioria, verifica-se a abordagem sobre a forma clínica da endocrinopatia. [18][19][20][21] De um modo geral, os resultados destas pesquisas evidenciam distúrbios na condutibilidade nervosa ao longo das vias auditivas no tronco encefálico, apontadas pelo prolongamento das latências absolutas das ondas e seus respectivos intervalos (I-III, III-V e I-V).…”

Autoimmune inner ear disease secondary to Hashimoto’s thyroiditis: a case report

“…In addition to thyroid dysfunction, HT can cause various otological symptoms. Although these abnormalities can occur as a direct consequence of hypothyroidism [1], it has been suggested that the circulating antithyroid autoantibodies can lead to T-cell mediated vestibulocochlear dysfunction. A review of the literature shows various case studies documenting the association of these two autoimmune entities [12–15] which demonstrate the existence of a clear relationship between thyroid autoimmunity and the inner ear damage, regardless of thyroid function.…”

“…Patients with Hashimoto’s thyroiditis (HT) are at higher risk of developing audiological abnormalities as compared to the healthy individuals [1]. This auditory dysfunction can be multifactorial as indicated by case studies done on HT.…”