What Is a Low TSH Level in a Woman?

TSH below 0.4 mIU/L is low. Women have unique causes.

Pregnancy Ranges

  • T1: 0.1–2.5
  • T2: 0.2–3.0
  • T3: 0.3–3.0

Causes in Women

  • Pregnancy (hCG effect)
  • Postpartum thyroiditis
  • PCOS
  • Graves’ disease
  • Overtreated hypothyroidism

When to Treat

  • Symptomatic — yes
  • Subclinical — depends on TSH and pregnancy plans
Source: American Thyroid Association, NLM MedlinePlus.

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