SEX-HORMONES REGULATE ABR LATENCY

In an effort to characterize more completely the influence of sex hormones on auditory brainstem response (ABR) latency, we evaluated the ABRs of normal male and female subjects and women with previously diagnosed endocrinologic syndromes. We describe ABR latency results from the following subjects: five normal males, nine normally cycling females on no hormonal therapy, nine females using oral contraceptive pills, five females with premature ovarian failure (POF) undergoing cyclic estrogen-progesterone replacement therapy, and five hyperandrogenized females with polycystic ovarian disease (PCOD) treated with the gonadotropin-releasing hormone agonist, Lupron depot, to suppress ovarian steroid production. All subjects were between 23 and 40 years of age. Serum levels of estradiol, progesterone, testosterone, prolactic, and gonadotropins (lutienizing hormone and follicle stimulating hormone) were measured to document the hormonal status of each of the subjects at the time of the ABR evaluation. Normal cycling females and females with POF underwent ABR testing during different phases of the same cycle. Male subjects and females using birth control pills were studied four times; baseline and then at 2-week intervals after the initiation of Lupron depot therapy. Increased ABR wave V peak latencies were found to be associated with elevated levels of estrogen or testosterone. We have previously reported a lengthening of ABR wave V peak latencies coincident with peak estrogen levels during the female cycle. Because testosterone is converted to estrogen by central neuroendocrine tissue to exert its effect on brain function, we postulated that increased latency in males is a result of the effect of aromatization of testosterone to estrogen in the central auditory pathway. This hypothesis would account for the slightly increased wave V peak latencies found in the PCOD females with elevated testosterone before treatment with Lupron to suppress ovarian androgen secretion. These findings suggest that neural conduction time is modified by changes in estrogen concentrations in the brainstem auditory pathway of both sexes.