How do letrozole and clomiphene citrate compare in ovulation induction for PCOS?

• A. Letrozole yields higher live birth rates with more antiestrogenic effects on the endometrium
• B. Clomiphene citrate yields the same endometrial thickness as letrozole but lower live birth rates
• C. Letrozole is ineffective for ovulation induction in PCOS
• D. Letrozole tends to yield higher live birth rates with fewer antiestrogenic effects on the endometrium

Answer: (D)

Letrozole and clomiphene citrate work differently to trigger ovulation in PCOS. Letrozole blocks estrogen production with an aromatase inhibitor, which lowers estrogen levels and increases FSH activity to stimulate ovulation, but it does not block estrogen receptors in the endometrium. That means the endometrium is less likely to become thin or unreceptive, leading to a more favorable environment for implantation. Evidence from randomized trials shows that letrozole tends to produce higher live birth rates than clomiphene while avoiding the antiestrogenic effects on the endometrium that clomiphene can cause. Clomiphene can induce ovulation, but its antiestrogenic action can thin the endometrium and alter cervical mucus, which can reduce the chance of implantation and pregnancy even when ovulation occurs.