http://www.biomedcentral.com/1472-6815/12/4
Abstract
Background
Tinnitus is a frequent, debilitating hearing disorder associated with severe emotional and psychological suffering. Although a link between stress and tinnitus has been widely recognized, the empirical evidence is scant. Our aims were to test for dysregulation of the stress-related hypothalamus-pituitary adrenal (HPA) axis in tinnitus and to examine ear sensitivity variations with cortisol manipulation.
Methods
Twenty-one tinnitus participants and 21 controls comparable in age, education, and overall health status but without tinnitus underwent basal cortisol assessments on three non-consecutive days and took 0.5 mg of dexamethasone (DEX) at 23:00 on the first day. Cortisol levels were measured hourly the next morning. Detection and discomfort hearing thresholds were measured before and after dexamethasone suppression test.
Results
Both groups displayed similar basal cortisol levels, but tinnitus participants showed stronger and longer-lasting cortisol suppression after DEX administration. Suppression was unrelated to hearing loss. Discomfort threshold was lower after cortisol suppression in tinnitus ears.
Conclusions
Our findings suggest heightened glucocorticoid sensitivity in tinnitus in terms of an abnormally strong glucocorticoid receptor (GR)-mediated HPA-axis feedback (despite a normal mineralocorticoid receptor (MR)-mediated tone) and lower tolerance for sound loudness with suppressed cortisol levels. Long-term stress exposure and its deleterious effects therefore constitute an important predisposing factor for, or a significant pathological consequence of, this debilitating hearing disorder.
...
Discussion
We report three novel findings that establish differences between tinnitus participants and controls in terms of cortisol hypersuppression, longer-lasting effects of the DEX test on basal cortisol levels, and hearing discomfort threshold. The first novel finding is that tinnitus participants had more strongly suppressed cortisol levels than controls after pharmacological challenge, despite similar basal cortisol levels. This is consistent with the normal diurnal and blunted response to psychosocial stress in tinnitus participants described in a previous study [23], and supports the hypothesis that tinnitus participants have greater sensitivity to HPA axis negative feedback. Hypersuppression in the presence of normal or near-normal basal cortisol levels has also been found in other clinical populations, such as patients with chronic fatigue syndrome [45-47] and burnout [48]. All these findings are consistent with the notion that basal cortisol and post-DEX cortisol suppression are mediated by two separate receptor feedback systems. More importantly, the suppression effect was independent of hearing loss. This is a key finding, because these factors are difficult to disentangle in tinnitus studies [19,23], and it argues for a true effect of tinnitus in addition to, but unrelated to, hearing loss. Our findings therefore directly link tinnitus to a stress-related disorder, and not just to a hearing-related disorder, as some recent population studies suggest [12,49].
...
In any case, considering tinnitus as a stress-related disorder by demonstrating HPA axis disturbance can open up new research avenues. For instance, studies of similar disorders show the same anomalies. There is a great need for new pharmacological targets in tinnitus [57], and a deeper understanding of HPA disturbance could lead to the development of pharmacotherapy targeting the HPA axis [58] as well as monitoring tools to assess the efficacy of tinnitus treatments and therapies.
Read more at the link....
Abstract
Background
Tinnitus is a frequent, debilitating hearing disorder associated with severe emotional and psychological suffering. Although a link between stress and tinnitus has been widely recognized, the empirical evidence is scant. Our aims were to test for dysregulation of the stress-related hypothalamus-pituitary adrenal (HPA) axis in tinnitus and to examine ear sensitivity variations with cortisol manipulation.
Methods
Twenty-one tinnitus participants and 21 controls comparable in age, education, and overall health status but without tinnitus underwent basal cortisol assessments on three non-consecutive days and took 0.5 mg of dexamethasone (DEX) at 23:00 on the first day. Cortisol levels were measured hourly the next morning. Detection and discomfort hearing thresholds were measured before and after dexamethasone suppression test.
Results
Both groups displayed similar basal cortisol levels, but tinnitus participants showed stronger and longer-lasting cortisol suppression after DEX administration. Suppression was unrelated to hearing loss. Discomfort threshold was lower after cortisol suppression in tinnitus ears.
Conclusions
Our findings suggest heightened glucocorticoid sensitivity in tinnitus in terms of an abnormally strong glucocorticoid receptor (GR)-mediated HPA-axis feedback (despite a normal mineralocorticoid receptor (MR)-mediated tone) and lower tolerance for sound loudness with suppressed cortisol levels. Long-term stress exposure and its deleterious effects therefore constitute an important predisposing factor for, or a significant pathological consequence of, this debilitating hearing disorder.
...
Discussion
We report three novel findings that establish differences between tinnitus participants and controls in terms of cortisol hypersuppression, longer-lasting effects of the DEX test on basal cortisol levels, and hearing discomfort threshold. The first novel finding is that tinnitus participants had more strongly suppressed cortisol levels than controls after pharmacological challenge, despite similar basal cortisol levels. This is consistent with the normal diurnal and blunted response to psychosocial stress in tinnitus participants described in a previous study [23], and supports the hypothesis that tinnitus participants have greater sensitivity to HPA axis negative feedback. Hypersuppression in the presence of normal or near-normal basal cortisol levels has also been found in other clinical populations, such as patients with chronic fatigue syndrome [45-47] and burnout [48]. All these findings are consistent with the notion that basal cortisol and post-DEX cortisol suppression are mediated by two separate receptor feedback systems. More importantly, the suppression effect was independent of hearing loss. This is a key finding, because these factors are difficult to disentangle in tinnitus studies [19,23], and it argues for a true effect of tinnitus in addition to, but unrelated to, hearing loss. Our findings therefore directly link tinnitus to a stress-related disorder, and not just to a hearing-related disorder, as some recent population studies suggest [12,49].
...
In any case, considering tinnitus as a stress-related disorder by demonstrating HPA axis disturbance can open up new research avenues. For instance, studies of similar disorders show the same anomalies. There is a great need for new pharmacological targets in tinnitus [57], and a deeper understanding of HPA disturbance could lead to the development of pharmacotherapy targeting the HPA axis [58] as well as monitoring tools to assess the efficacy of tinnitus treatments and therapies.
Read more at the link....