ESTROGEN INFLUENCES AUDITORY BRAIN-STEM RESPONSES DURING THE NORMAL MENSTRUAL-CYCLE

We evaluated the impact of the menstrual cycle on auditory brainstem response (ABR) latency in nine normally cycling women. Subjects (age 23-40 years) using no hormonal therapy were recruited and underwent ABR testing during four different phases of the same menstrual cycle: early follicular (cycle days 1 to 3); mid-cycle (cycle days 12 to 15); mid-luteal (cycle days 17 to 22), and premenstrual (cycle days 25-27). Cycles were verified by basal body temperature, an&serum estrogen (E2), progesterone (P), and gonadotropin levels. A control group of nine women (age 23-40 years) on oral contraceptives (Nordette-28) was also studied four times during a pill cycle. Results show a significant increase in the latency of wave III and wave V peak latencies and in the I-V interpeak interval associated with a high estrogen state at the mid-cycle phase. No statistically significant variations in latency were found in the birth control pill group. These data suggest the existence of brainstem auditory neural pathways that are sensitive to fluctuations in E2 levels during the menstrual cycle.