VHOSPITAL.CLINIC · Differential Diagnosis
Hypothyroidism vs PCOS (Polycystic Ovary Syndrome)
Clinical comparison — shared symptoms, key differences, distinguishing diagnostic tests, treatment pathways, and when to seek urgent evaluation.
Condition Overview
Condition A
Hypothyroidism
Hypothyroidism occurs when the thyroid gland doesn't produce enough thyroid hormone. This slows metabolism and causes fatigue, weight gain, cold intolerance, constipation, and depression. Hashimoto's thyroiditis is the most common cause.
Condition B
PCOS (Polycystic Ovary Syndrome)
Polycystic ovary syndrome (PCOS) is a hormonal disorder common among women of reproductive age, causing irregular periods, excess androgen levels, and polycystic ovaries. It is associated with insulin resistance and increased risk of diabetes and heart disease.
Shared Symptoms — Why They're Confused
Both conditions present with 3 overlapping symptoms, making clinical differentiation essential.
Key Clinical Differences
Hypothyroidism
- Weight gain, fatigue, cold intolerance, constipation
- Irregular periods from anovulation
- Dry skin, hair loss, bradycardia
- TSH elevated; Free T4 low
PCOS (Polycystic Ovary Syndrome)
- Irregular or absent periods (oligomenorrhoea/amenorrhoea)
- Androgen excess: hirsutism, acne, alopecia
- Polycystic ovaries on ultrasound
- Insulin resistance; metabolic syndrome features
Distinguishing Diagnostic Tests
| Test | Hypothyroidism | PCOS (Polycystic Ovary Syndrome) |
|---|---|---|
| TSH + Free T4 | Elevated TSH, low Free T4 — hypothyroidism can mimic PCOS | Normal thyroid function — PCOS is not thyroid-driven |
| Androgens (testosterone, DHEAS) | Normal androgens — no hyperandrogenism | Elevated free testosterone and/or DHEAS — androgen excess |
| Pelvic ultrasound | Normal ovaries — no polycystic morphology | ≥12 follicles per ovary or ovarian volume >10 ml |
Treatment Approaches
Hypothyroidism
- •Levothyroxine replacement resolves menstrual irregularity in most cases
PCOS (Polycystic Ovary Syndrome)
- •Combined OCP for cycle regulation and androgen suppression
- •Metformin for insulin resistance
- •Letrozole/clomiphene for ovulation induction
When Doctors Consider Each Diagnosis
🔵 Consider Hypothyroidism when:
- →Cold intolerance, bradycardia, elevated TSH, no hyperandrogenism, normal ovaries
🟢 Consider PCOS (Polycystic Ovary Syndrome) when:
- →Hirsutism, acne, normal TSH, polycystic ovaries, insulin resistance
Explore Each Condition in Detail
Related Clinical Pages
Hypothyroidism
PCOS (Polycystic Ovary Syndrome)
Medical References
Content on this page is informed by evidence-based clinical sources including:
- World Health Organization (WHO)Global health guidance and disease classification
- National Health Service (NHS)UK clinical guidelines and patient information
- National Institute for Health and Care Excellence (NICE)Evidence-based clinical practice guidelines
- Centers for Disease Control and Prevention (CDC)US public health data and clinical recommendations
- PubMed – NCBIPeer-reviewed biomedical literature and clinical studies
- Cochrane LibrarySystematic reviews and meta-analyses in evidence-based medicine
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