A 28-year-old woman with PCOD presents with oligomenorrhea and hirsutism. She has a BMI of 32 kg/m² and fasting insulin level of 18 mIU/mL (elevated). She desires fertility. Which is the drug of choice for ovulation induction in this patient?

Explanation

## Rationale for Letrozole as Drug of Choice for Ovulation Induction in PCOD **Key Point:** Letrozole (an aromatase inhibitor) is currently the **drug of choice for ovulation induction in PCOD**, including in obese and insulin-resistant patients, based on the landmark NICHD/PPCOS II trial (Legro et al., NEJM 2014) and endorsed by ACOG, ESHRE/ASRM (2023 International Evidence-Based Guideline for PCOS). **High-Yield:** Letrozole produces higher live birth rates and ovulation rates compared to clomiphene citrate in PCOD, with a lower risk of multiple pregnancies. It is particularly advantageous in obese patients (BMI >30) and those with insulin resistance. ### Why Letrozole Over Other Options? | Drug | Role in PCOD | First-line for Ovulation Induction? | |---|---|---| | **Letrozole** | Aromatase inhibitor; transiently lowers estrogen → FSH surge → mono-follicular development | ✅ YES — current DOC | | Clomiphene citrate | SERM; blocks estrogen receptors → FSH rise; older first-line agent | ❌ Superseded by letrozole | | Metformin | Insulin sensitizer; adjunctive; restores ovulation in ~30% | ❌ Not primary ovulation inducer | | Gonadotropins | Reserved for clomiphene/letrozole failure | ❌ Second/third line | ### Mechanism of Letrozole 1. Inhibits aromatase enzyme → reduces peripheral estrogen synthesis 2. Removes negative feedback on hypothalamus/pituitary → increased FSH secretion 3. Promotes mono-follicular development (lower multiple pregnancy risk vs. clomiphene) 4. No anti-estrogenic effect on endometrium or cervical mucus (unlike clomiphene) ### Clinical Context - This patient has **BMI 32** and **elevated fasting insulin** — features of insulin resistance - Metformin is an important **adjunct** to improve insulin sensitivity and may enhance response to letrozole, but it is **not** the drug of choice for ovulation induction - The question specifically asks for "drug of choice for **ovulation induction**" — this is letrozole **Clinical Pearl:** Per ESHRE/ASRM 2023 PCOS Guidelines and Berek & Novak's Gynecology (16th ed.), letrozole has replaced clomiphene citrate as the first-line pharmacological agent for ovulation induction in anovulatory PCOS/PCOD. Metformin may be added as adjunctive therapy, especially in insulin-resistant patients. [cite: Berek & Novak's Gynecology 16th ed.; ESHRE/ASRM International Evidence-Based Guideline for PCOS 2023; Legro RS et al., NEJM 2014]