Tri-est and Bi-est Tri-est and Bi-est are formulations in which the predominant estrogen is estriol. The typical formulations contain 80% estriol. Typically Tri-est contains 2 mg of estriol, 0.25 mg of estradiol, and 0.25 mg of estrone, and Bi-est contains 2 mg of estriol and 0.5 mg of estradiol. It should be noted that these names refer only to the types of estrogen used, and the specific amounts of each can vary. These particular formulations are often marketed as the most “natural” form of estrogen therapy because they contain either two or all three forms of naturally occurring estrogens. The following factors should be noted:
Tri-est and Bi-est are not formulated in naturally occurring ratios or quantities.
Although Tri-est and Bi-est are only 20% E2 or E2 plus E3, the dose of these more potent estrogens are significant (i.e., 0.5 mg).
Although a certain combination of E1/E2/E3 may prove to have benefits over other forms of hormone therapy and should be explored, this research does not exist.
Estriol Vaginal Cream Estriol vaginal cream was studied in women who had recurrent urinary tract infections. This randomized controlled trial compared vaginal estriol cream with placebo for 8 months of treatment and showed a significant reduction in urinary tract infections (0.5 vs.
5.9 per patient year). In the treatment arm, there was a reduction in vaginal pH from 5.5 to 3.8 compared with no decline in the placebo group (101). In a randomized controlled trial of 27 women on hormone therapy with urogenital atrophy, the addition of vaginal estriol shortened the latency period for urinary symptoms (102).
The effect of vaginal estriol cream on the endometrium was evaluated in a study examining long-term use for urogenital atrophy. Patients were given 0.5 mg of estriol cream vaginally for 21 days, then twice weekly for 12 months. Hysteroscopic and histologic examinations were performed at baseline, 6 months, and 12 months. Complete endometrial atrophy occurred in all patients (N = 23) (103). This pilot study needs to be performed in a larger patient population, but its findings are promising.