Endocrine - Thyroid Development
From Embryology
Lecture - Head Development | UNSW Embryology - Thyroid Development
- Functions from wk10, required for neural development, stimulates metabolism (protein, carbohydrate, lipid), reduced/absence = cretinism (see abnormalities)
Hormones - (amino acid derivatives) Thyroxine (T4), Triiodothyronine (T3)
Thyroid Development
- thyroid median endodermal thickening in the floor of pharynx, outpouch – thyroid diverticulum
- tongue grows, cells descend in neck
- thyroglossal duct - proximal end at the foramen cecum of tongue thyroglossal duct
- thyroid diverticulum - hollow then solid, right and left lobes, central isthmus
Thyroid Timeline
- 24 days - thyroid median endodermal thickening in the floor of pharynx, outpouch – thyroid diverticulum
- Week 11 - colloid appearance in thyroid follicles, iodine and thyroid hormone (TH) synthesis
growth factors (insulin-like, epidermal) stimulates follicular growth
Fetal Thyroid Hormone
- Initial secreted biologically inactivated by modification, late fetal secretion develops brown fat
- Iodine deficiency- during this period, leads to neurological defects (cretinism)
- Birth - TSH levels increase, thyroxine (T3) and T4 levels increase to 24 h, then 5-7 days postnatal decline to normal levels
