The thyroid is a small gland in the front of your neck just below your voice box (larynx). It is made up of two parts called lobes. The lobes are connected by a thin bridge of thyroid tissue called the isthmus.
The thyroid gland is part of the endocrine system. This system makes hormones that help to control and influence the way your body functions. Your thyroid gland makes the following hormones:
- thyroxine (T4)
These keep your body functioning at the right speed.
If your thyroid gland does not make enough hormones, your body’s cells will work slower than normal. You will feel tired and may put on weight more easily. This is called hypothyroidism, myxoedema or an underactive thyroid.
If your thyroid gland makes too many hormones, your body’s cells will work faster than normal. This is called hyperthyroidism, thyrotoxicosis or an overactive thyroid. You may lose weight, feel hungrier than normal, and feel shaky and anxious. Your heartbeat may be faster than normal or irregular.
A part of your brain called the hypothalamus senses if the levels of T3 and T4 in your blood are too low. If they are, it sends thyroid-releasing hormones (TRH) into your blood. The rising level of TRH makes another gland in the brain, called the pituitary gland, release thyroid-stimulating hormone (TSH). TSH then stimulates the thyroid gland to produce more T3 and T4.
Most people who have a thyroid gland cancer have normal levels of T3 and T4.
The thyroid gland needs a regular supply of iodine to produce thyroid hormones. We get iodine from our diet. It is mainly found in fish, seafood and dairy products.
Calcitonin helps to control the amount of calcium in the blood. It works together with another hormone called parathyroid hormone (PTH), which is made in the parathyroid glands. These are four very small glands behind the thyroid gland. Calcium helps your muscles and nerves work, builds strong bones and helps your blood to clot.
The lymphatic system helps to protect us from infection and disease. It also drains lymph fluid from the body’s tissues before returning it to the blood. The lymphatic system is made up of fine tubes called lymphatic vessels that connect to groups of lymph nodes throughout the body.
Lymph nodes (sometimes called lymph glands) are small and bean-shaped. They filter bacteria (germs) and disease from the lymph fluid. When you have an infection, lymph nodes often swell as they fight it.
Thyroid cancer cells can sometimes spread to the lymph nodes in the neck and chest.