The Role of Plasma Melatonin and Vitamin C and B12 in the Development of Idiopathic Tinnitus

This is not new, but I wanted to post this here in case it wasn't reported yet:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3645155/

Discussion
The generation of tinnitus have been linked to damage to the central and peripheral auditory systems, even in cases where an impairment could not be detected by audiometry. Impairment of the auditory system cannot be detected by audiometry if it only causes tinnitus without an accompanying hearing loss. In this study, the main finding is that low plasma melatonin and vitamin B12 have significant correlation with the development of tinnitus among the elderly. Melatonin is a neurohormone produced centrally by the pineal gland; it regulates the sleep-wake cycle by inducing sleepiness and reducing body temperature through its effects on the circadian clock. Several workers have reported that melatonin is useful in the treatment of tinnitus, even in cases associated with sleep disturbance.

Concerning vitamin B12, our finding is supported by the report of Shemesh et al. They reported that the incidence of vitamin B12 deficiency is significantly higher among patients with tinnitus and noise-induced hearing loss (47%) compared with those with noise induced hearing loss alone and normal subjects who exhibited vitamin B12 deficiency in 27% and 19%, respectively. In addition they reported some improvement in tinnitus and associated complaints in 12 patients following vitamin B12 replacement therapy. These suggest a relationship between vitamin B12 deficiency and dysfunction of the auditory pathway; hence they recommended that routine vitamin B12 serum levels be determined when evaluating patients for chronic tinnitus.

The presence of tinnitus as the only features in these subjects with low plasma vitamin B12 suggest that perhaps tinnitus may be one of the early features of the various neurological abnormalities associated with B12 deficiencies. In this case, the tinnitus is thought to be due to auditory nerve malfunction. Our impression is that correction of the plasma levels of these markers may lead to reversal of tinnitus, however, this needs to be studied in the future. Among other studies of the role of biochemical markers in tinnitus, Baguley 30 identified endogenous dynorphins to be responsible for the excitatory function of glutamate within the cochlea, thus, mimicking the action of sodium salicylate in increasing spontaneous neural activity. Similarly, Simpson and Davies postulated that persistent tinnitus was due to role of serotonin and they suggested that disrupted or modified 5 - Hydroxy Triptamine (5HT) function might cause a reduction in auditory filtering abilities and in tinnitus habituation.

Other workers have also found that Zinc influences the biophysiological function of neural membranes and transmission such that in the cochlea, levels of zinc are higher than any other organs of the body and the patients showed a significant decrement in their tinnitus after taking zinc. All these reports might be evidence that research into the biology of tinnitus is still evolving and so the application of the findings in the treatment of this condition.

Notably, the values for the serum levels of these biomarkers from this study are low compared with previously published figures. The mean serum levels of vitamin B12 of 151.0–300.0 pmol/L, serum vitamin C value greater than 28µmol/L and melatonin peak value of 70.6+/−14 pg/mL were reported as normal. In our study Melatonin ranged between 5.1 pg/mL and 30.2pg/mL while serum Vitamin C level was between 0.3 µmol/mL and 1.2 µmol/mL and vitamin B12 ranged between 25.4 pmol/L and 71.6 pmol/L.

The low figures in this study may be further evidence of the prevalent low level of nutritional health in our population compared to others. However, the method of storage and assay may also account for the difference in the values reported. However, we conclude from this study that low plasma melatonin and vitamin B12 have significant correlation with the development of subjective idiopathic tinnitus among the elderly.

This finding suggests the need to study the role of correction of these markers in the reversal or control of tinnitus.