“ Ovulation induction” refers to the use of medications to stimulate the ovaries to release at least one egg. We induce ovulation in woman who would not otherwise ovulate normally. Most women with ovulation disorders can be induced to ovulate given the correct type and dose of medication.
A common condition associated with “anovulation” (no spontaneous ovulation) or “oligo-ovulation” (infrequent ovulation) is called “Polycystic Ovarian Syndrome” (PCOS). PCOS is associated with a variety of disturbances such as androgen excess (androgens are the class of hormones responsible for male secondary sexual characteristics) and resistance to insulin. The hormones that normally stimulate ovulation, FSH and LH, are present but in abnormal amounts so that normal ovulation is impaired. This leads to multiple small cystic structures in the ovaries and is the basis for the term Polycystic Ovarian Syndrome.
Another type of ovulation disorder, termed “Hypothalamic Amenorrhea” is distinguished by low or absent FSH and LH leading to low ovarian hormone production. Common causes of hypothalamic amenorrhea include low body fat due to excess exercise or weight loss, and stress.
Ovarian failure can also result in low ovarian hormone production. In this case, FSH is elevated. While this is considered natural when it occurs at the normal age of menopause, it is abnormal if ovarian failure occurs prior to the age of 40 years. This is termed “Premature Ovarian Failure” and, unfortunately, cannot be corrected with ovulation inducing medications.
The reason for the distinction between these disorders is that each requires a different approach to ovulation induction. Premature ovarian failure typically responds poorly to any medication, hypothalamic amenorrhea only responds to gonadotropin (FSH/LH) stimulation and anovulation/oligo-ovulation (PCOS) usually responds to either clomiphene citrate (Clomid) or gonadotropin stimulation. Clomiphene citrate is an inexpensive oral medication with limited side effects and a low rate of multiple pregnancy. Gonadotropins are more expensive, injectable medications that are capable of stimulating the release of large numbers of eggs even with careful monitoring. The attributes of gonadotropins that make them more risky for OI are precisely the characteristics that make them ideal for IVF where we want to retrieve as many eggs as possible.
When used appropriately, both medications are safe and effective treatments to induce a woman to ovulate. We often have to try several doses before we find the most effective dose that will result in single egg ovulation. In suitable cases, ovulation rates exceed 95% given the time and patience required to determine the best medication and dose.
Several years ago, a concern developed about an increased risk of ovarian cancer in women who had used ovulation stimulating drugs. Further studies suggest that the increased risk of ovarian cancer is due the underlying in fertility disorder rather than to the medications used to treat it. In addition, even one successful pregnancy lowers the ovarian cancer risk to below that seen in the general population. Despite these reassurances, we discourage the long term use of any ovulation inducing medication without periodic reevaluation of its utility.
Within the last few years, other medications have been identified that can improve the results of ovulation induction in women with PCOS. These medications can be used in conjunction with standard ovulation inducing medications or can be tried alone. These include metformin (Glucophage) and letrozole (Femara).