A 28-year-old woman from Delhi presents with a 3-year history of irregular menstrual cycles (ranging from 45 to 90 days) and progressive hirsutism over the face and abdomen. She reports difficulty conceiving for the past 18 months despite regular unprotected intercourse. On examination, BMI is 26 kg/m², acne is present on the face, and there is dark velvety skin (acanthosis nigricans) over the neck and axillae. Pelvic ultrasound shows bilateral ovaries with multiple small follicles (12–15 per ovary) and increased ovarian stroma. Fasting blood glucose is 98 mg/dL, and fasting insulin is 18 mIU/L. LH:FSH ratio is 3.2:1. What is the most likely diagnosis?

Explanation

## Diagnosis: Polycystic Ovary Syndrome (PCOS) with Insulin Resistance ### Clinical Features Present | Feature | Finding | Significance | |---------|---------|---------------| | **Menstrual irregularity** | 45–90 day cycles | Anovulation due to abnormal follicle development | | **Hirsutism** | Face and abdomen | Hyperandrogenism (elevated testosterone/androstenedione) | | **Acanthosis nigricans** | Neck and axillae | Marker of insulin resistance | | **BMI** | 26 kg/m² | Overweight; 50–70% PCOS patients are obese | | **Acne** | Facial | Androgen-driven sebaceous gland activity | | **Infertility** | 18 months | Anovulation prevents ovulation | ### Diagnostic Criteria (Rotterdam 2003) **Diagnosis requires ≥2 of 3:** 1. **Oligo/anovulation** — irregular cycles ✓ (present) 2. **Clinical or biochemical hyperandrogenism** — hirsutism + acne ✓ (present) 3. **Polycystic ovaries on ultrasound** — ≥12 follicles per ovary ✓ (present) **Key Point:** All three Rotterdam criteria are met in this patient, making PCOS the definitive diagnosis. ### Biochemical Findings **High-Yield:** - **LH:FSH ratio 3.2:1** — elevated LH drives excessive androgen production by theca cells - **Fasting insulin 18 mIU/L** — markedly elevated (normal <12), indicating **insulin resistance** - **Fasting glucose 98 mg/dL** — normal, but with elevated fasting insulin = insulin resistance (HOMA-IR ≈ 4.4, abnormal) - **Acanthosis nigricans** — clinical hallmark of severe insulin resistance **Clinical Pearl:** Insulin resistance is present in 50–70% of PCOS patients, even in lean women. It drives hyperandrogenism via enhanced LH signalling and reduced SHBG (sex hormone–binding globulin), increasing free testosterone. ### Why PCOS Fits This Case ```mermaid flowchart TD A[Insulin resistance]:::outcome --> B[↑ LH secretion]:::outcome A --> C[↓ SHBG synthesis]:::outcome B --> D[↑ Theca cell androgen production]:::outcome C --> E[↑ Free testosterone]:::outcome D --> F[Hyperandrogenism]:::outcome E --> F F --> G[Hirsutism, acne, male-pattern baldness]:::action A --> H[Abnormal follicle maturation]:::outcome H --> I[Anovulation]:::outcome I --> J[Irregular cycles + infertility]:::action ``` ### Differential Exclusion **Why not hypothyroidism?** TSH would be elevated; menstrual irregularity is usually oligomenorrhoea/amenorrhoea (not polycyclic); no hirsutism or acanthosis nigricans; acne is rare. **Why not Cushing syndrome?** Would show proximal muscle weakness, purple striae, easy bruising, hypertension, hypokalemia; 24-hour urinary cortisol and low-dose dexamethasone suppression test would be abnormal; acanthosis nigricans is not typical. **Why not ovarian tumour?** Androgen-secreting tumours (Sertoli–Leydig cell, lipoid cell) cause **severe** hyperandrogenism with testosterone often >200 ng/dL; rapid onset of virilization; unilateral ovarian mass on imaging; no insulin resistance or acanthosis nigricans. **High-Yield:** The combination of **oligo-anovulation + hyperandrogenism + polycystic ovaries + insulin resistance + acanthosis nigricans** is pathognomonic for PCOS.