A 32-year-old woman with secondary infertility and irregular menstrual cycles (40–60 days) is suspected to have anovulation. Before initiating ovulation induction, which investigation is most appropriate to assess her ovarian reserve and determine the starting dose of gonadotropins?

## Ovarian Reserve Assessment Before Ovulation Induction ### Clinical Context In a woman with anovulation and irregular cycles, assessing ovarian reserve is essential before initiating gonadotropin therapy to predict response and avoid ovarian hyperstimulation syndrome (OHSS). Multiple tests exist, but AMH is increasingly preferred. ### Investigation of Choice: Anti-Müllerian Hormone (AMH) **Key Point:** AMH is a marker of ovarian reserve that reflects the number of primordial and small antral follicles. It is cycle-independent and can be measured at any time, making it practical in anovulatory women with irregular cycles. **High-Yield:** AMH levels correlate with ovarian reserve: - **AMH >3 ng/mL:** Good ovarian reserve, normal response expected - **AMH 1–3 ng/mL:** Normal to reduced reserve, standard dose recommended - **AMH <1 ng/mL:** Poor ovarian reserve, consider high-dose gonadotropins or alternative strategies - **AMH >5 ng/mL:** Risk of PCOS and excessive response; consider lower starting dose **Clinical Pearl:** AMH is produced by granulosa cells of preantral and small antral follicles, making it a direct measure of the follicle pool available for recruitment. ### Why AMH Is Superior in This Case 1. **Cycle-independent:** Can be measured any day; critical in anovulatory women with unpredictable cycles. 2. **Stable throughout cycle:** No significant fluctuation like FSH or LH. 3. **Predicts ovarian response:** Strong correlation with number of oocytes retrieved and cycle outcome. 4. **Guides dosing:** Allows personalized gonadotropin dosing before starting treatment. 5. **No need for serial testing:** Single measurement provides actionable information. ### Comparison of Ovarian Reserve Tests | Test | Timing | Cycle-Dependent? | Predicts Response | Practical in Anovulation? | | --- | --- | --- | --- | --- | | **AMH** | Any day | No | Excellent | **Yes** | | FSH (day 3) | Early follicular | Yes | Good | No (requires regular cycles) | | Antral follicle count (AFC) | Day 2–3 | Yes | Excellent | No (requires cycle day identification) | | CCCT | Days 5–7 | Yes | Moderate | No (requires regular cycles) | | Inhibin B | Day 3 | Yes | Moderate | No (requires regular cycles) | **Warning:** In anovulatory women with irregular cycles, day 3 FSH and AFC are impractical because cycle day cannot be reliably identified. AMH eliminates this problem. ### Algorithm for Ovarian Reserve Assessment and Dosing ```mermaid flowchart TD A[Anovulation suspected<br/>Irregular cycles]:::outcome --> B[Measure AMH<br/>at any time]:::action B --> C{AMH level?}:::decision C -->|AMH >5 ng/mL| D[High reserve<br/>PCOS risk<br/>Start low-dose FSH<br/>Monitor closely]:::action C -->|AMH 1-3 ng/mL| E[Normal reserve<br/>Standard dose FSH<br/>Routine monitoring]:::action C -->|AMH <1 ng/mL| F[Poor reserve<br/>High-dose FSH or<br/>Consider alternatives]:::action D --> G[Ovulation induction<br/>± IUI/IVF]:::outcome E --> G F --> G ``` ### Additional Considerations **Mnemonic: AMH — Anytime, Measured, Helpful** - **Anytime:** No cycle day requirement - **Measured:** Direct reflection of follicle pool - **Helpful:** Guides personalized dosing and predicts response [cite:Fertil Steril 2015 ASRM Guideline; Textbook of Reproductive Medicine 3e Ch 15]