What does the Thyroid gland do?
In basic terms, the thyroid gland is an endocrine gland that produces hormones (thyroxine (T4), triiodothyronine (T3) & calcitonin) that regulates your metabolic rate and to a degree your blood calcium. It is a butterfly shaped gland that sits just in front of your windpipe in your neck (right where you would tie a bow tie).
The activity of the thyroid gland is under the control of the hypothalamus/pituitary gland in your brain by a negative feedback loop. In simple terms, the thyroid is likened to the boiler in your house which is controlled by the thermostat (hypothalamus/pituitary gland). The higher the thermostat is set the harder the boiler works and the hotter the radiators get. To prevent the boiler from exploding the thermostat monitors the heat and set the boiler settings accordingly (click 'Thyroid Control System').
What does an Underactive Thyroid gland mean?
An underactive thyroid is a thyroid gland that is not producing enough thyroid hormones for your bodys need. In other words the boiler is broken and the radiators are not hot enough. So when your doctor checks your blood levels, you may find you have a high TSH level but a low thyroxine level. This is like turning the thermostat up (TSH) to make the boiler work harder to keep the house warm. To treat the underactive thyroid you must take thyroxine. Your doctor can then measure your TSH level in your blood to ensure you get the right amount.
The most common cause of underactive thyroid (hypothyroidism) is autoimmune where your body's normal defence turns against the thyroid gland and slowly destroys it. Other causes of hypothyroidism include taking medications like amiodarone or lithium and in some cases following surgery or radioactive iodine treatment for hyperthyroidism. The symptoms of hypothyroidism include fear of cold, lethargy, depression, poor memory, weight gain, hair loss, deepening of voice, constipation, infertility in the young and even dementia in the old.
Surgery for hypothyroidism is unusual although sometimes goitres may develop from this necessitating surgery to improve cosmesis.
What does a Nodular Goitre mean?
This simply means the thyroid gland is enlarged. It can be caused by either a single lump (solitary thyroid nodule) or many lumps (multinodular) like a bunch of grapes. Nodules in thyroid are very common. About 50% of population will harbour thyroid nodules by age 50yrs and between 5 and 10% of population will have a palpable thyroid nodule. About 10% of solitary nodules and dominant nodules in a multinodular goitre will be malignant. Most of these solitary and multinodular goitres cause little to no symptoms which include obstructive symptoms (breathing, swallowing), hyperactivity (see overactive thyroid gland), unsightliness. A history of a rapidly enlarging nodule, hoarse voice, presence of multiple enlarged lymph glands is suggestive of malignancy.
Assessement of these nodules should include a thyroid function blood test and a referral to see a specialist. You may have an ultrasound test to confirm the nodule being cystic or solid. The most important test is a fine needle aspiration to draw some cells from the thyroid nodule to check under a microscope. Based on the result of these tests, your doctor can advice you whether it is safe to leave the nodule alone or to have an operation.
Surgery is advised if there is suspicion or proof of cancer, presence of obstructive symptoms, goitre growing into the chest, overactive nodule and cosmesis.
What does an Overactive Thyroid gland mean?
An overactive thyroid (hyperthyroidism) gland is producing excess thyroid hormones to your bodys need. In other words the boiler is on high and the radiators are red hot! When your doctor checks your blood levels, the TSH is low or may not be detectable and the thyroxine level is elevated. This is the same as trying to cool down by turning the thermostat to zero (TSH) but finding the boiler stuck on high heat!
The most common cause of hyperthyroisism is Graves disease. This affects mainly women and is often accompanied by eye problems (staring eyes). Other causes include a toxic nodular goitre (no eye problems) commonly seen in older people with lumpy goitres (multinodular) where one of these lumps have become overactive. Viral infections of the thyroid and medications like amiodarone may also cause hyperthyroidism. People with hyperthyroidism will often have goitres (enlarged thyroid gland) and are frequently described as `having ants in their pants! Their symptoms include trembling hands, restlessness, fast pulse rate, palpitations, weight loss and intolerance to heat, sweaty skin, diarrhoea, infrequent menstruation.
Treatment is aimed at reducing or stopping the activity of the thyroid gland, in other words switch off or remove the boiler. This is achieved by taking antithyroid medicines (eg. carbimazole, propylthiouracil) to stop your thyroid gland making hormones (turning the gas/electricity mains off). This typically takes up to two months to take effects. Occasionally your doctor may give you thyroxine if the thyroid activity is fully blocked and medications to control the palpitations and increase heart rate (eg atenolol). Most people stay on antithyroid medication for 12 to 24 months before it is stopped. About 50% of patients will have a relapse necessitating further definitive treatment.
Definitive treatment is aimed at permanently inactivating the thyroid gland. This can be achieved medically (radioactive iodine) or surgically. In other words we can either break the boiler or remove the boiler completely. Medical treatment involves drinking a radioactive iodine solution which is concentrated in the thyroid gland and destroying it. Typically it takes three to six months after treatment before it takes effect. Surgery is preferred in patients with a very large goitre or severe eye problems as radioactive iodine may worsen the eye protrusion. Surgery in expert hands is a fast and safe way to rapidly achieve control of hyperthyroidism (see thyroidectomy).
What if I have Thyroid Cancer?
Thyroid cancers are rare and the majority are eminently curable. Between 5-10% of thyroid nodules are cancers and the majority belong to the `well differentiated thyroid cancers.
Rarer forms of thyroid cancers include medullary thyroid cancer, thyroid lymphoma and anaplastic thyroid cancer. With the exception of thyroid lymphoma and anaplastic cancer, surgery is the mainstay of treatment for thyroid cancers. Radioactive iodine treatment is given for most types of thyroid cancers after removing the thyroid. This acts like magic bullets that seeks out and destroy any microscopic thyroid cancer cells that might have spread.
What does Thyroid Surgery entail?
You may be recommended to have either half (lobectomy) or the entire thyroid (total thyroidectomy) removed. Surgery is carried out under general anaesthetics. The average size of the wound is between 5 and 10cm depending on the size of the goitre.
The operation in experienced hands is safe with few problems. As with any surgery there is a very low risk of bleeding and infection. Specific problems associated with thyroid surgery include injury to the recurrent laryngeal nerve (RLN) and parathyroid glands. There are two nerves (RLN) that lie close to either side of the thyroid gland that moves your vocal cords. Surgery may stun these nerves rendering them temporarily out of action in 10% of cases (1 in 10). In most people this results in a hoarse (sexy) voice for several weeks/months before full recovery. On very rare occasions (1 in 100) these nerves may be permanently damaged. Beside the RLNs there are four parathyroid glands (two on either side of the thyroid) that control the blood calcium levels. Surgery can bruise or inadvertently remove these glands rendering the blood calcium to drop after surgery (hypocalcaemia) necessitating calcium supplements. Most cases will recover between 3 and 6 months with about 1% needing permanent calcium replacement.
Surgery for thyroid cancer is more extensive than routine thyroidectomy for benign disease. Most thyroid cancers, with the exception of small cancers, will require a total thyroidectomy with removal of the surrounding lymph glands. More extensive lymph node resection may be required for certain types and stage of cancers. Unfortunately this also increases the risk of injury to the RLNs, parathyroid glands and permanent hypocalcaemia.
What happens after Thyroidectomy?
Thyroxine replacement is required in anyone who has had a total thyroidectomy. The dose is dependent on your body mass but is usually between 100 and 200mcg. Your weight should not fluctuate once the correct dose is reached and you will only require an annual check up thereafter.
Patients with thyroid cancer will be put on T3 replacement until the radioactive iodine treatment. This is much shorter acting than thyroxine and is taken three times daily.
Thyroxine is commenced following radioactive iodine ablation. Thyroxine replacement in thyroid cancer is targeted at suppressing the TSH (turning the thermostat off) to minimise risk of recurrence. In addition, a blood test to measure thyroglobulin, a substance made by thyroid cells is also required annually. Patients who had thyroid cancers will require long term specialist follow-up.