Thyroid gland

Author: Shahidul Islam, M.D., Ph.D. (see Authors page)

Revised: 11 January 2017, last major update March 2009

Copyright: (c) 2003-2017,, Inc.

PubMed search: embryology [title] thyroid

Related topics: Ultimobranchial body development in thyroid gland
Cite this page: Embryology. website. Accessed March 30th, 2017.
Definition / General
  • Week 3 (day 24) of embryonic life: appears as midline vesicular structure at foramen cecum (base of tongue) from ductlike invagination of ventral pharyngeal endoderm that grows caudally (descends) to become thyroglossal duct in neck; thyroglossal duct then atrophies
  • Week 7: finishes descent along midline; two lateral analgens develop from 4th - 5th branchial pouch, which contains ultimobranchial body; midline and lateral portions of thyroid fuse
  • Week 9: cords and plates of follicular cells are formed
  • Week 10: small follicular lumina appear
  • Weeks 11 -12: colloid secretion appears
  • Week 14: well developed follicles are lined by follicular cells and contain thyroglobulin containing colloid in lumina
  • Early growth and development is independent of TSH (Best Pract Res Clin Endocrinol Metab 2008;22:57)
Micro Images

Images hosted on PathOut server:

14 week fetus (AFIP images):

Thyroid gland location

Minute follicles, some with lumina

Images hosted on other servers:

Invagination of thyroid bud in mouse

Additional References