Patterns of luteinizing and follicle-stimulating hormone pulsatility in menopausal women: Correlation with plasma testosterone level and vasomotor instability episodes

OBJECTIVE: The purpose of this study was to test the hypothesis that subtle differences among postmenopausal women can be detected by careful analysis of plasma luteinizing hormone and follicle-stimulating hormone pulses. STUDY DESIGN: Twelve postmenopausal women not receiving estrogen therapy were admitted for continuous blood withdrawal at the rate of 1 ml/min. Aliquots of 3 ml of pooled blood were collected every 3 minutes for 3 hours for the measurement of plasma luteinizing hormone and follicle-stimulating hormone. Estradiol, estrone, free testosterone, androstenedione, and dihydrotestosterone were measured from pooled specimens. Concomitantly, continuous recordings of peripheral blood flow and peripheral temperature from the opposite arm were obtained to detect vasomotor instability episodes. RESULTS: Analysis of gonadotropin pulses revealed a single pattern of plasma follicle-stimulating hormone but two distinct patterns of luteinizing hormone frequency and amplitude. One group of six women had a low mean (±SEM) interpulse interval frequency of 0.8 ± 0.26 (p< 0.005) and a high mean amplitude of 18.4 ± 1.8 IU/L (p< 0.05). The second group of six women had a high mean interpulse interval frequency of 3.5 ± 0.34 and a low mean amplitude of 12.2 ± 1.8 IU/L luteinizing hormone pulses. Women with this pattern had more inter-vasomotor instability episode intervals (3.5 ± 1.6) than did women with low frequency and high amplitude (1.3 ± 0.5, p< 0.001). Women with low frequency and high amplitude pulses had higher plasma levels of estrone (266 ± 33 nmol/L), testosterone (2.3 ± 0.7 mmol/L), and free testosterone (8.0 ± 0.1 pmol/L, p< 0.05). CONCLUSION: There are subgroups of postmenopausal women with different patterns of luteinizing hormone pulsatility. This difference can be explained by higher steroid levels in women with low frequency and high amplitude pulses.