Glutathione S-transferase M1, T1, and P1 polymorphisms as susceptibility factors for noise-induced temporary threshold shift.

The generation of reactive oxygen species (ROS) is thought to be part of the mechanism underlying noise-induced hearing loss (NIHL). Glutathione is an important cellular antioxidant that limits cell damage by ROS. We aimed to determine the effect of genetic polymorphisms of glutathione S-transferase (GST) T1, GSTM1, and GSTP1, on temporary threshold shift (TTS) in 58 noise-exposed male workers from a steel factory. The pre-shift hearing impairment at high frequency (HF, average of 3, 4, and 6kHz) was 30.7dB HL (S.D.=19.3). The amount of daily noise exposure was 83.0dBA (S.D.=5.0). Noise-induced TTS at HF by pure-tone audiometry (PTA) was related to the daily noise exposure (p<0.05). Based on combinatory analysis, we found that individuals carrying all genotypes with GSTT1 null, GSTM1 null, and GSTP1 Ile(105)/Ile(105) were more susceptible to NIHL. These results suggest that pre-shift hearing impairment and daily noise exposure had impacts on TTS at HF by PTA. In addition, GST genetic polymorphisms may modify the susceptibility to noise-induced TTS.