Developmental exposure to @entity3215 ( @entity14774 ) reduces circulating thyroid hormone concentrations and causes hearing deficits in XXXX .

@entity1 @entity1375 @entity66 @entity2167 @entity3935 @entity5241 @entity14774 @entity1017 @entity3215 @entity35 @entity1954
@entity1375 causes growth @entity66 , and @entity2167 in @entity1 and animals. Therefore, environmental toxicants, such as @entity3215 ( @entity3215 ), may secondarily affect these endpoints via @entity3935 . In this study, Long-Evans @entity35 were given @entity14774 (po), at 0, 1, 4, or 8 mg/kg from Gestation Day 6 through Postnatal Day (PND) 21. We evaluated the offspring at various age intervals for circulating thyroid hormone concentrations [thyroid-stimulating hormone, and free and total @entity1954 (T3) and thyroxin (T4)], body weight, eye opening, survival, motor activity development, auditory startle response, and auditory thresholds. Circulating T4 concentrations were sharply reduced in a dose-dependent fashion in @entity5241 -exposed groups at PND 1, 7, 14, 21, and 30 but recovered to control levels by PND 45. Moderate reductions in T3 concentrations were apparent in the 4 and 8 mg/kg groups on PND 21 and 30. @entity1017 and early eye opening were apparent in the treated pups; by weaning, pup mortality was 20% in the 4 mg/kg group and 50% at the highest dose. Motor activity was also transiently reduced in 15 day old offspring from the 8 mg/kg group. At this dose, animals showed @entity2167 at PND 24, but not when tested as adults. Importantly, @entity14774 caused permanent @entity2167 (20-30 dB threshold shift) at the lowest frequency tested (1 kHz) in both the 4 and 8 mg/kg groups, whereas auditory thresholds were not significantly affected at higher frequencies (4, 16, 32, or 40 kHz). These data indicate that while some effects of @entity14774 exposure are dissimilar to @entity1375 (e.g., age of eye opening), effects on hormone levels and body weight are comparable. @entity2167 in @entity5241 -treated animals is a novel finding and may reflect the effects of thyroid hormone disruption on the development of the cochlea.
