Thyroid-stimulating hormoneNutrition library
LibraryBlood markersThyroid
Thyroid-stimulating hormone
Thyroid-stimulating hormone screens thyroid axis function — pregnancy-specific trimester reference ranges apply.
Subclinical hypo- or hyperthyroidism affects miscarriage risk, blood pressure, and fetal neurodevelopment. hCG can suppress TSH in early pregnancy.
How to read it
Always interpret with free T4 (and free T3 if measured). Trimester-specific lab ranges beat generic adult cut-offs.
Trimester context
| Stage | For the mother | For the baby |
|---|---|---|
| First trimester | hCG-driven TSH suppression is common — use pregnancy reference intervals. | Maternal thyroid hormone crosses the placenta early. |
| Second trimester | Levothyroxine dose often needs upward adjustment. | Fetal thyroid begins autonomous function mid-pregnancy. |
| Third trimester | Uncontrolled hypothyroidism raises obstetric complication risk. | Late adequacy supports neurodevelopment. |