A 22-year-old woman with a history of menarche at age 13 presents with secondary amenorrhea for 4 months. She reports recent weight loss of 8 kg over 3 months, increased exercise, and high stress from competitive sports training. Pelvic ultrasound is normal. FSH, LH, and prolactin are within normal limits. All of the following are recognized causes of secondary amenorrhea in this clinical context EXCEPT:

## Clinical Context: Functional Secondary Amenorrhea This patient has **secondary amenorrhea with normal pelvic ultrasound and normal gonadotropins/prolactin** — suggesting a **functional (hypothalamic) etiology** rather than ovarian or pituitary pathology. ### Why PCOS Is the Answer **Key Point:** Polycystic ovary syndrome (PCOS) is characterized by **hyperandrogenism** and **polycystic ovarian morphology on ultrasound**. The patient's ultrasound is explicitly stated as **normal**, and there is no mention of hirsutism, acne, or elevated androgens. PCOS typically presents with: - Irregular/absent periods - **Polycystic ovaries on ultrasound** (≥12 follicles per ovary) - **Elevated androgens** (clinical or biochemical) - Normal or mildly elevated LH:FSH ratio In this case, the **normal ultrasound excludes PCOS** as a diagnosis. ### Correct Causes of Secondary Amenorrhea in This Scenario | Diagnosis | Mechanism | Findings in This Patient | | --- | --- | --- | | **Hypothalamic amenorrhea** | Energy deficit from weight loss + exercise + stress | ✓ Weight loss, increased exercise, stress; normal imaging | | **Thyroid dysfunction** | Altered TRH → altered GnRH pulsatility | ✓ Can present with amenorrhea; normal FSH/LH | | **Hyperprolactinemia** | Dopamine antagonism → suppressed GnRH | ✓ Causes amenorrhea; prolactin normal here but could be elevated | | **PCOS** | Hyperandrogenism + ovulatory dysfunction | ✗ Requires polycystic ovaries on ultrasound; ultrasound is normal | **High-Yield:** The **diagnostic triad of PCOS** (Rotterdam criteria) requires ≥2 of: 1. Oligo-/anovulation 2. Clinical or biochemical hyperandrogenism 3. **Polycystic ovaries on ultrasound** A normal ultrasound **excludes PCOS** as a diagnosis. **Clinical Pearl:** In a young athlete with recent weight loss, stress, and amenorrhea — think **hypothalamic amenorrhea** (functional). PCOS would require polycystic ovarian morphology on imaging. **Mnemonic for causes of secondary amenorrhea:** **CHASM** - **C**ontracept ion (hormonal) - **H**ypothalamic (stress, weight loss, exercise) - **A**ndrogen excess (PCOS, adrenal) - **S**tructura l (Asherman's) - **M**etabolic (thyroid, prolactin)