The thyroid gland is a butterfly-shaped gland found in your neck, just in front of your larynx (voice-box). It produces a hormone which is carried in the bloodstream, and which is essential for the normal functioning of every single cell in your body.
This hormone – called T4 – helps regulate energy, maintain body temperature and generally assists with the normal functioning of other organs such as muscles, brain and heart. Because of its various biological functions, disturbances of thyroid hormone can have wide-ranging effects.
Problems can arise if the thyroid gland becomes more or less active than normal. An overactive gland is called hyperthyroidism, and an underactive gland is called hypothyroidism. There are a number of different causes for each of these conditions.
WHAT BLOOD TESTS CAN TELL US
Hormone production is regulated by the brain. Thyroid Stimulating Hormone (TSH) from the brain instructs the thyroid gland to produce thyroid hormone, T4, using dietary Iodine. In the tissues where it is needed, T4 is converted into more biologically active T3. When enough T3 and T4 are in circulation, TSH levels are reduced to normal. If your thyroid gland is overactive, there will be too much T3 and T4 in your blood, and only traces of TSH. If your thyroid is underactive, there will be very low levels of T3 and T4 in circulation, but very high levels of TSH as your brain tries to stimulate your sluggish gland to produce more hormone.
TYPES OF DISORDERS
Various conditions can affect the thyroid, but there are essentially only two outcomes: the gland becomes either over-active or under-active. Some autoimmune conditions can result in alternating over- and under-activity. In any thyroid disorder there may be little or no change in the appearance of the gland, but swelling with or without nodules may occur.
An underactive thyroid will result in a general slowing down of all body processes. Symptoms could thus include fatigue, weight gain, constipation, fuzzy thinking, low blood pressure, fluid retention, depression, general body pain and slow reflexes. Destruction of the thyroid by surgery, radiation or your own antibodies (Hashimoto’s disease) can cause hypothyroidism, which is treated by replacing the missing hormone. Autoimmune hypothyroidism (Hashimoto’s disease) is best managed by a specialist.
The symptoms of hyperthyroidism are due to an overstimulated metabolism resulting from excess thyroid hormone. Common symptoms include anxiety, insomnia, rapid weight loss, diarrhoea, high heart rate, high blood pressure, eye sensitivity/bulging and vision disturbances. Autoimmune hyperthyroidism (Graves’s disease) is also often found.
Excess hormone levels are reduced in several different ways: e.g.
• antithyroid drugs
• radioactive iodine treatment (RAI or radioidine ablation)
• surgical removal of all or part of the thyroid, called thyroidectomy
• symptom control using beta blocker medication
Goiter — an enlarged thyroid –may cause a tender or tight feeling in the neck or throat, hoarseness or coughing, and difficulty swallowing or breathing.
Symptoms caused by nodules vary with how biologically active they are: some cause no symptoms, while others may cause difficulty swallowing, a feeling of fullness, pain or pressure in the neck, a hoarse voice, or neck tenderness. Some overactive nodules trigger hyperthyroid-like symptoms such as palpitations, insomnia, weight loss, anxiety, and tremors.