? 2012 Pearson Education, Inc. The Thyroid Gland ? Lies anterior to thyroid cartilage of larynx ? Consists of two lobes connected by narrow isthmus ? Thyroid follicles ? Hollow spheres lined by cuboidal epithelium ? Cells surround follicle cavity that contains viscous colloid ? Surrounded by network of capillaries that ? deliver nutrients and regulatory hormones ? accept secretory products and metabolic wastes Figure 18-10 ? 2012 Pearson Education, Inc. The Thyroid Gland: Thyroid hormones ? Thyroglobulin (Globular Protein) ? Synthesized by follicle cells ? Secreted into colloid of thyroid follicles ? Molecules contain the amino acid tyrosine ? Thyroxine (T4) ? ?pro-hormone? ? Also called tetraiodothyronine