Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 9 5 2025 04 26 212 216 Mahmoud Ali Kaykhaei Health Promotion Research Center, Zahedan University of Medical Sciences, Zahedan, Iran. Shahin Nosratzehi Department of Internal Medicine, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran. 2025 01 03 2025 03 10 Silent thyroiditis during pregnancy is an under-recognized clinical condition and a rare case, often manifesting as transient hypothyroidism. We report a 23-year-old woman at 8 weeks of gestation who presented with newly diagnosed hypothyroidism [TSH = 85 mIU/L (0.4–4.5), FT4 = 0.4 ng/dL (0.7–2.5), and anti-TPO = 78 IU/mL (up to 16)]. Thyroid function tests had been normal eight months prior. Levothyroxine (LT4) therapy was initiated, restoring euthyroidism. Treatment was discontinued postpartum, and the patient maintained normal thyroid function for over one year. Our case is unique in that silent thyroiditis occurred unusually early in pregnancy and differed from the more common postpartum cases. Silent thyroiditis should be considered in pregnancy-related hypothyroidism, particularly when prior thyroid function was normal. Prompt diagnosis and treatment can prevent adverse maternal and fetal outcomes. https://crcp.tums.ac.ir/index.php/crcp/article/view/1012 https://crcp.tums.ac.ir/index.php/crcp/article/download/1012/687