Tamoxifen - Ovulation Induction

Tamoxifen is an anti-oestrogen and it is generally considered to increase fertility rates in a similar way to clomiphene. In contrast to clomiphene, however, tamoxifen does not increase follicular phase FSH and LH levels, although there is an increase in oestradiol levels and luteal phase progesterone. It has, therefore, been postulated that tamoxifen improves follicular development by direct action on the ovary rather than through the hypothalamic-pituitary axis (menstrual cycles). We usually start with 20mg daily from the second to the sixth day and build up to a maximum of 80mg. When used for short periods, tamoxifen does not appear to be associated with any increased risk of either ovarian or endometrial malignancy.

Early studies indicated similar success rates between tamoxifen and clomiphene. In one series of 66 anovulatory patients, both drugs achieved pregnancy rates of 80% within nine months. When clomiphene fails to achieve ovulation or pregnancy, tamoxifen may prove to be effective and vice versa.

Some authorities have recommended tamoxifen as their first choice for women with polycystic ovary syndrome (PCOS). The argument has been that PCOS is associated with relatively high levels of LH and this seems to reduce the chance of conception and increase the chance of miscarriage. Unlike clomiphene , tamoxifen does not further increase LH levels. Metformin may supersede tamoxifen and clomiphene as the first choice agent in PCOS (12).

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