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. 2021 Jun 11;9:669354. doi: 10.3389/fcell.2021.669354

FIGURE 1.

FIGURE 1

Human thyroid development. Timeline of thyroid development. Thyroid organogenesis covers the embryonic and fetal periods. Thyroid fate determination happens prior to weeks 4. Specific transcription factors (NKX2.1, PAX8, FOXE1, and HHEX) are expressed at week 4. Thyroid progenitor cells migration occurs at weeks 4–7; TSHR (TSH receptor) is expressed at week 8. Thyroid functional differentiation: weeks 7–11, colloid appearing at weeks 10–11, when genes such as TPO, TG, NIS, and DUOX, coding for proteins involved in thyroid function are expressed. Thyroid maturation (GW 12 – 1 months after birth or later). TSH is present at week 10 at low concentration in fetal plasma, at week 20 it increases to reach a maximum level between weeks 20 and 30. Fetal TSH receptors become responsive to TSH around week 20. Week, gestational week. E, embryonic day. TR, gestational trimester. In yellow: gestational weeks covered by our study. Conc, conception.