Overview
Diseases of the thyroid gland are common and affect up to 10% of people over their lifetime.1 The most common problem is reduced thyroid hormone production (hypothyroidism), which is often due to an autoimmune disease called Hashimoto’s Thyroiditis. Graves’ disease is the most common cause of increased thyroid hormone production (hyperthyroidism) and is also autoimmune in nature. Thyroid disease predominantly affects females and often arises during child-bearing years. Both conditions are treated with medication (Thyroxine in the case of hypothyroidism and anti-thyroid drugs such as carbimazole or propylthiouracil for most causes of hyperthyroidism), but some patients with hyperthyroidism will require more definitive treatments such as surgery or radio-iodine treatment.
Introduction
The thyroid gland consists of two lobes which lie below the strap muscles in the anterior neck, joined in the midline by a band of tissue known as the thyroid isthmus. In healthy adults, the thyroid weighs between 10-20 g.2 The thyroid is made up of follicles, which consist of a single layer of epithelial cells that surround a central lumen filled with clear colloid, surrounded by a network of capillaries.3
The regulation of thyroid function is tightly controlled by the hypothalamic-pituitarythyroid axis due to a classical endocrine negative feedback loop. Thyroid stimulating hormone (TSH, or thyrotropin) is released by the anterior pituitary in response to thyrotropin-releasing hormone (TRH) and stimulates thyroid hormone production, thyroxine (T4) & triiodothyronine (T3), in the thyroid gland. As the circulating concentration
