11.9 Synthesis of Thyroid Hormone

Colloid

Large molecule, mainly protein, to which capillaries are relatively impermeable; also, part of the inner structure of the thyroid gland

Follicles

Composed of an enclosed sphere of epithelial cells surrounding the colloid

Iodide Trapping

Active transport of iodide from extracellular fluid across the thyroid follicular cell membrane, followed by transport of iodide into the colloid of the follicle

Organification

Attachment of iodine to tyrosine within thyroglobulin during synthesis of thyroid hormone

Pendrin

Sodium-independent chloride/iodide transporter

Thyroglobulin

Large protein precursor of thyroid hormones in colloid of follicles in thyroid gland; storage form of thyroid hormones

Thyroid Peroxidase

Enzyme within the thyroid gland that mediates many of the steps of thyroid hormone synthesis

Thyroxine (T4)

Tetraiodothyronine; iodine-containing amine hormone secreted by thyroid gland

Triiordothyronine (T3)

Iodine-containing amine hormone secreted by thyroid gland or produced in target cells from T4