Ovulation Physiology · Anovulation
Mitwally MF et al., 2001 · Fertil Steril
To use aromatase inhibition for induction of ovulation in women in whom clomiphene citrate (CC) treatment was unsuccessful. Prospective trial in infertility patients treated with CC. Two tertiary-referral infertility clinics associated with the Division of Reproductive Sciences, University of Toronto. PATIENT(S): Twelve patients with anovulatory polycystic ovary syndrome (PCOS) and 10 patients with ovulatory infertility, all of whom had previously received CC with an inadequate outcome (no ovulation and/or endometrial thickness of < or =0.5 cm). INTERVENTION(S): The aromatase inhibitor letrozole was given orally in a dose of 2.5 mg on days 3-7 after menses. MAIN OUTCOME MEASURE(S): Occurrence of ovulation, endometrial thickness, and pregnancy rates. RESULT(S): With CC treatment in patients with PCOS, ovulation occurred in 8 of 18 cycles (44.4%), and all ovulatory cycles for the women included in this study had endometrial thickness of < or =0.5 cm. In 10 ovulatory patients, 15 CC cycles resulted in a mean number of 2.5 mature follicles, but all cycles had endometrial thickness of < or =0.5 cm on the day of hCG administration. With letrozole treatment in the same patients with PCOS, ovulation occurred in 9 of 12 cycles (75%) and pregnancy was achieved in 3 patients (25%). In the 10 patients with ovulatory infertility, letrozole treatment resulted in a mean number of 2.3 mature follicles and mean endometrial thickness of 0.8 cm. Pregnancy was achieved in 1 patient (10%). CONCLUSION(S): Oral administration of the aromatase inhibitor letrozole is effective for ovulation induction in anovulatory infertility and for increased follicle recruitment in ovulatory infertility. Letrozole appears to avoid the unfavorable effects on the endometrium frequently seen with antiestrogen use for ovulation induction.
Ovulation Physiology · Follicular Development
Healey S et al., 2003 · Fertility and sterility
To investigate the effects of letrozole in patients undergoing superovulation with gonadotropins and IUI. Retrospective analysis. Academic teaching hospital. PATIENT(S): Women younger than 40 years of age with patent fallopian tubes and infertility of more than 1 year in duration who were undergoing IUI and gonadotropin therapy. INTERVENTION(S): Gonadotropins alone administered from day 3 or a combination of letrozole, 5 mg/d on day 3 to 7, and gonadotropins starting on day 5 of the menstrual cycle. Ultrasonography was performed before initiation of treatment, on day 9 of menstrual cycle, and as required thereafter until the dominant follicle reached 18 mm in diameter. Ovulation was triggered with 10,000 IU of hCG, and IUI was performed 24 and 48 hours later. MAIN OUTCOME MEASURE(S): Gonadotropin requirements, endometrial thickness, number of follicles, and pregnancy rate. RESULT(S): All 205 IUI treatment cycles conducted from March 2001 to March 2002 were included. Gonadotropins alone were used in 145 cycles and combination therapy was used in 60 cycles. Patients cotreated with letrozole required fewer gonadotropin administrations (median difference, 300 IU [95% confidence interval (CI), 225-375 IU]), developed more follicles larger than 14 mm (median difference, 1 follicle [95% CI, 1-2 follicles), and had a thinner endometrium (median difference, 1 mm [95% CI, 0.4-1.6 mm]). The pregnancy rate did not differ between patients using gonadotropin alone and those using gonadotropin plus letrozole (20.9% vs. 21.6%). CONCLUSION(S): The addition of letrozole to gonadotropins decreases gonadotropin requirements, increases the number of pre-ovulatory follicles and decreases endometrial thickness, without a negative effect on pregnancy rates.
Ovarian Hormones · Estrogen
Kilic-Okman T et al., 2003 · Fertil Steril
To compare the effects of letrozole and clomiphene citrate in the rat in terms of number of ovarian follicles; endometrial thickness; and serum levels of E2, FSH, LH, and T. Controlled prospective study. University research laboratory. ANIMAL(S): Thirty sexually mature female Wistar-Albino rats that were 20 weeks of age. INTERVENTION(S): Letrozole, 5 mg/kg of body weight daily (10 rats); clomiphene citrate, 100 microg/kg daily (10 rats); or saline solution, 2 mL/d (10 rats). After 2 days, rats were euthanized and ovariectomized. MAIN OUTCOME MEASURE(S): Number of mature follicles, endometrial thickness, and serum levels of hormones. RESULT(S): Mean levels of FSH, LH, E2, and T; number of mature follicles; and ovary size differed among the groups, whereas the mean endometrial thickness did not differ. CONCLUSION(S): In rats, the effect of letrozole on follicular maturation is similar to that of clomiphene citrate.
Ovarian Hormones · Estrogen
la Marca A et al., 2002 · Fertil Steril
To investigate the effects of reduction of insulin resistance and hyperinsulinemia associated with the polycystic ovary syndrome (PCOS) on FSH-stimulated ovarian aromatase activity. Prospective study. Academic health center, Siena, Italy. PATIENT(S): Twenty women 18 to 26 years of age in whom PCOS was diagnosed on the basis of oligomenorrhea or amenorrhea and hyperandrogenemia. INTERVENTION(S): Recombinant FSH was administered. The next day, therapy with metformin (500 mg t.i.d.) was begun. After 35 to 40 days of treatment, the pretreatment protocol was repeated. MAIN OUTCOME MEASURE(S): Plasma levels of estradiol (E(2)), androstenedione (A), and testosterone (T). The ratios of basal levels and areas under the curve (AUCs) of products and substrates were compared before and after metformin administration to detect differences in aromatase activity. RESULT(S): Metformin treatment was associated with significant reduction in basal free testosterone plasma levels, insulin plasma levels, and insulin response to oral glucose tolerance testing. Administration of FSH was followed by a significantly lesser E(2) response after metformin therapy than before this therapy. The ratios of AUC(E2) to AUC(A) and to AUC(T), indicative of aromatase activity in response to FSH, were significantly lower after metformin therapy than before. CONCLUSION(S): Metformin therapy in women with PCOS is associated with a reduction in aromatase activity in response to FSH. Insulin affects production of both androgen and estrogen. Insulin therefore plays a central role in regulating the activity of thecal and granulosa cells.