Auditory brain stem response in experimentally induced hypothyroidism in albino rats.

In order to elucidate the relationship between the auditory function and the thyroid state, experiments were designed to study the effect of hypothyroidism on the onset of auditory brain stem response (ABR) in 26 adult myxedematous albino rats. A state of hypothyroidism was induced by daily oral administration of 6-N-propyl-2-thiouracil (PTU). In 23 out of 26 rats we found minor changes in the amplitudes of all ABR waves without any correlation with the rats' T4 variation. We noted a conspicuous, dynamic, and reversible change in the amplitude of the third wave (N3) of ABR which correlates directly with the thyroxin (T4) levels in the rats' blood. The electrophysiological finding in this report indicates a lesion in the auditory tracts in the brain stem but mainly in the second main relay station of the central auditory pathway, i.e., the superior olivary complex.