Thyroid tissue is strange tissue. It’s delicate and fatty, with a rich blood supply. It’s vulnerable to toxins such as mercury, which accumulate in the thyroid.
Even more strange is the histology or microstructure of the gland. It’s composed of little bubbles or sacs (follicles) that house the oxidative reactions of iodine transfer and hormone production. The surrounding tissue is shielded from these mini-cauldrons by only a single layer of cells. Imagine a pile of water balloons full of hazardous chemicals, and you get a sense of the precariousness of this gland. When tissue damage occurs, the body responds with repair and growth, and unfortunately at times over-growth, resulting in nodules and goitre.