The Induction of Hypothyroidism during Gestation Decreases Outer Hair Cell Motility in Rat Offspring

Abstract

Introduction Perinatal hypothyroidism has a negative repercussion on the development and maturation of auditory system function. However, its long-term effect on auditory function remains unsettled. Objective To evaluate the effect of prenatal hypothyroidism on the auditory function of adult offspring in rats. Methods Pregnant Wistar rats were given the antithyroid drug methimazole (0.02% -1-methylimidazole-2-thiol– MMI) in drinking water, ad libitum, from gestational day (GD) 9 to postnatal day 15 (PND15). Anesthetized offspring from MMI-treated dams (OMTD) and control rats were evaluated by tympanometry, distortion product otoacoustic emission (DPOAE), and auditory brainstem response (ABR) at PNDs 30, 60, 90, and 120. Results Our data demonstrated no middle ear dysfunction, with the OMTD compliance lower than that of the control group. The DPOAE revealed the absence of outer hair cells function, and the ABR showed normal integrity of neural auditory pathways up to brainstem level in the central nervous system. Furthermore, in the OMTD group, hearing loss was characterized by a higher electrophysiological threshold. Conclusion Our data suggest that perinatal hypothyroidism leads to irreversible damage to cochlear function in offspring.

Causal relationship between hypothyroidism and the risk of hearing loss: A bidirectional two-sample Mendelian randomization study

“…For instance, some genetic or chromosomal disorders can also present with hypothyroidism and hearing loss at the same time, including Pendred syndrome variants in the SLC26A4 gene (37)(38)(39), Woodhouse-Sakati Syndrome variants in the DCAF17 gene (40), Down syndrome (41), and TBL1X mutations (42). In animal experiments, Oliveira et al (43) observed that perinatal hypothyroidism leads to irreversible damage to cochlear function in offspring rats. Others found that the congenital hypothyroid mouse displayed consistent morphologic abnormalities of the stereocilia on both inner and outer hair cell systems.…”