Читать книгу The Healthy Thyroid: What you can do to prevent and alleviate thyroid imbalance - Patsy Westcott - Страница 19

Like all of the glands in the body, the thyroid is regulated and controlled by the pituitary gland, the small, pea-sized gland attached to the brain often referred to as the ‘master gland’. The pituitary gland orchestrates the entire hormonal symphony but is, in turn, driven by the hypothalamus, to which it is joined by a short stalk of nerve fibres. This hypothalamic – pituitary – thyroid gland connection is a key junction through which chemical messages are carried to and from the brain and the body.

Levels of thyroid hormone are regulated by a feedback loop that operates between the hypothalamus, pituitary and thyroid glands. Anything that increases the body’s need for energy – such as a fall in temperature or a bout of exercise – will provoke the hypothalamus to secrete a chemical messenger called thyrotropin-releasing hormone (TRH) to trigger the pituitary to secrete a messenger chemical called thyrotropin or thyroid-stimulating hormone (TSH), which stimulates the thyroid to secrete thyroid hormone. As the thyroid releases increasing amounts of TH, chemical messages are eventually passed on to the hypothalamus to inhibit production of TRH and, in turn, TSH.

This chemical round-robin means that TSH levels are a highly sensitive indicator of thyroid activity and can provide an early clue that the thyroid is not working as it should. This is why the TSH test is a key investigation in checking the health of your thyroid (see Chapter 4).