Thyroid Histology

Basic Components
  • Thyroid Follicles:
    • These spherical structures are the basic functional units of the thyroid gland that produce thyroid hormones. They are of variable size and are tightly packed, composing the bulk of the Thyroid Gland.
  • Thyroid Follicular Epithelial Cells:
    • These compose the simple cuboidal epithelium which forms the outside layer of each thyroid follicle. They play a key role in both the biochemical synthesis and regulated secretion of thyroid hormones.
  • Thyroid Colloid
    • This is the amorphous, acellular, proteinacious center of each thyroid follicle and is largely composed of thyroglobulin.
  • Parafollicular Cells (AKA "C Cells")
    • Parafollicular Cells are scattered among the follicular epithelial cells within the follicular epithelium and can be distinguished by their slightly lighter staining on H&E. Parafollicular Cells are not involved in thyroid hormone synthesis or regulation and instead control synthesis and regulation of calcitonin.
  • Thyroid Capsule
    • A fibrous capsule encloses the entire thyroid gland. From it extends thin collagenous septa which divide the thyroid follicles into lobules.