Nestled in the tissues of your neck is a small, unassuming organ that wields enormous power over your body: the thyroid. Like the operations manager in a company, its role is to make sure that the cells in your body are working properly.
The two main thyroid hormones are T3 (triiodothyronine) and T4 (thyroxine). A thyroid that is functioning normally produces approximately 80% T4 and about 20% T3.
Thyroid also produces calcitonin, which helps control blood calcium levels.
The pituitary gland and hypothalamus both control the thyroid. When thyroid hormone levels drop too low, the hypothalamus secretes TSH Releasing Hormone (TRH), which alerts the pituitary to produce thyroid stimulating hormone (TSH). The thyroid responds to this chain of events by producing more T3 and T4.
The thyroid’s main role in the endocrine system is to regulate your metabolism, which is your body’s ability to break down food and convert it to energy.
Hyperthyroidism is caused by too much thyroid hormone. People with hyperthyroidism are often sensitive to heat, hyperactive, and eat excessively.
Hypothyroidism is a common condition characterized by too little thyroid hormone. People with hypothyroidism may experience sensitivity to cold, little appetite, and an overall sluggishness.
An enlargement of the thyroid gland is called a ‘goitre’. A shortage of iodine in the diet is a common cause of goitre. Goiter can also result from autoimmune conditions (Hashimoto's thyroiditis and Graves' disease)
"Autoimmune disorders" of the thyroid gland are the most common cause of thyroid dysfunction. These autoimmune disorders are caused by abnormal proteins, (called antibodies), and the white blood cells which act together to stimulate or damage the thyroid gland.
Graves’ disease(hyperthyroidism) is due to a unique antibody called "thyroid stimulating antibody" which stimulates the thyroid cells to grow larger and to produce excessive amounts of thyroid hormones.
Hashimoto’s disease (hypothyroidism) is an autoimmune condition in which white blood cells and antibodies attack the thyroid gland.