Tibolone, transdermal estradiol or oral estrogen–progestin therapies: Effects on circulating allopregnanolone, cortisol and dehydroepiandrosterone levels

The aim of the present study was to evaluate, in healthy postmenopausal women, the impact of tibolone (2.5 mg), transdermal estradiol (50 μg) (TE) and different oral estrogen–progestin regimens, conjugated equine estrogens (0.625 mg) plus medroxyprogesterone acetate (5 mg) (CEE + MPA) and estradiol (2 mg) plus norethisterone acetate (1 mg) (E2 + NETA) on circulating estradiol, progesterone, allopregnanolone, cortisol and dehydroepiandrosterone (DHEA) levels. Blood samples were collected before and after 1, 3, 6 and 9 months of treatment in 85 postmenopausal women. Estradiol levels increased (p < 0.001) in the TE, CEE + MPA and E2 + NETA groups after 1 month of therapy, but did not change in the tibolone group during the entire follow-up period. Both E2 + NETA and tibolone treatments induced an increase in progesterone levels (p < 0.05) after 1 year of therapy. Allopregnanolone levels showed an increase in all estrogen-based groups, being significant after 3 months of treatment (p < 0.01). Patients receiving tibolone showed a significant increase in allopregnanolone levels at 3 months (p < 0.05), but lower than in the other groups. Cortisol levels decreased significantly in the TE and CEE + MPA groups after 6 months and 12 months of treatment, respectively. Neither tibolone nor E2 + NETA treatments modified circulating cortisol levels. DHEA levels significantly (p < 0.05) decreased after 6 months of TE or estrogen–progestin therapies independently of the presence or the type of progestin used. In contrast, DHEA remained stable throughout the 12 months of treatment with tibolone. The increase of allopregnanolone, a steroid with sedative and anxiolytic properties, in response to these different treatments could underlie, at least in part, the central effects that hormone replacement therapy and tibolone have on anxiety, mood and behavior. Unlike estrogen-based therapy, tibolone treatment did not reduce the DHEA milieu in the menopause, and thus did not enhance the androgen deficiency syndrome in postmenopausal women.