Flow resistance in carotid and middle cerebral arteries in postmenopausal women: A comparative study of tibolone and continuous combined hormone replacement therapy

Objective: The study sought to compare the vascular resistance and serum lipids of postmenopausal women assigned to tibolone therapy or continuous combined hormone replacement therapy. Design: This was a 6-month, prospective, single-blind, single-center, randomized study. A total of 50 healthy postmenopausal women were enrolled. At study end, 40 women had completed a 6-month follow-up. The first group (23 subjects) received conjugated equine estrogens (CEE) 0.625 mg/day and medroxyprogesterone acetate (MPA) 5 mg/day. The second group (17 subjects) received tibolone 2.5 mg/day. The pulsatility and resistance indexes of the carotid and middle cerebral arteries, and serum lipid profiles were monitored. Results: Comparisons demonstrated that there were no significant differences between the groups in terms of changes in the pulsatility index (PI) and the resistance index (RI) of the common carotid artery (CCA), internal carotid artery (ICA), and middle cerebral artery (MCA) within the study period. Both treatments effectively reduced the total cholesterol level and with no significant differences found between the two regimens. However, in comparing the two groups, we found that high-density lipoprotein (HDL) cholesterol levels were significantly lower in the tibolone group at either 3 months or 6 months after treatment, whereas a significantly higher triglycerides level was observed in the CEE + MPA group after 3 months of treatment. Low-density lipoprotein (LDL) cholesterol levels indicated no significant differences between the two groups after treatment. Conclusions: The study demonstrated that major neck and cerebral vascular impedance was not influenced significantly by either regimen. Nonetheless, lipid profiles were affected differently by tibolone and by continuous combined CEE + MPA. However, whether or not these findings might modify cardiovascular risk is still unknown.