Assessment of the effectiveness of postmenopausal tibolone therapy on neural functions by measuring visual evoked potentials: a placebo-controlled study

OBJECTIVE: To assess the effect of hormone replacement therapy on neural transmission in postmenopausal women using tibolone by a non-invasive, objective way. STUDY DESIGN: In a randomised, 3 cycle, placebo-controlled study, neurovisual transmission in optic pathways were evaluated by measuring visual evoked potentials (VEP). After neuroophtalmologic examination, eligible subjects were randomised into two groups. Treatment group (n=38) were given tibolone 2.5mg daily continuously for 3 months and control group (n=20) were treated with placebo. A baseline VEP measurement before the treatment and then at the end of first, second and third month were obtained by the EMG-evoked system in the Department of Neurology, University of Celal Bayar, Manisa, Turkey. RESULTS: Data from 31 women from treatment group and 16 from control group were available for evaluation. The mean P(100) latency values, which indicate the transition time period between the optic stimuli and electrical change recorded on the occipital area by the skin electrodes, have showed a significant decrease for the study group (from 100.39+/-0.58 to 97.90+/-0.65 ms, P<0.01) at the end of the first month of treatment according to the baseline values. This difference between two groups has remained constant during the study period. CONCLUSION: The change in latency measurements of VEP, reflecting the functional status in optic pathways from retina to occipital cortex were significantly different in the treatment group than in that of control. We concluded that a facilitating effect of tibolone was observed on neurovisual transmission.