File:Human thyroid system and neural development.jpg

Human Thyroid System Development

Timeline of human thyroid system and brain development from conception to birth. Estimation of neurogenesis adapted from Bayer et al. (1993).

• Development of the human thyroid gland begins in the third week of gestation.
• GD 16-17 - embryonic thyroid is visible as an outgrowth in the floor of the primitive buccal cavity (the site of the future pharynx).
  • Additional lateral contributions to the embryonic thyroid originate from a portion of the fourth pharyngeal pouches; these lateral contributions are the origin of the C-cells, which produce calcitonin.
• GD29 - thyroglobulin (TBG), the precursor protein upon which thyroid hormone is produced and stored, is initially detected in thyroid follicle cells.
• GD45-50 - thyroid gland tissues merge and migrate to their final location.
• GD70 - thyroid gland is well developed; it begins concentrating iodide and producing thyroid hormone at this time (3).
• GW11 - TBG levels are detected in fetal serum as thyroid follicle cells mature, and continues to increase through gestation.

GD = gestation day GW = gestational week TBG = thyroglobulin

Reference

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