Medihub - Medical Information - Endocrinology

What is Hyperthyroidism ?

‘Hyper-thyroidism’ is simply an over-active (hyper) thyroid gland. The thyroid gland is located just in front of the voice box (trachea) at the front of the neck. It is ‘butterfly shaped’ , the 2 wings represented by the 2 lobes of the thyroid gland (right and left) joined in the middle by the isthmus. An over-active thyroid gland produces a higher than normal amount of thyroid hormones (thyroxine and tri-iodothyronine, or T4 and T3 for short) which control body metabolism.

The most common cause of hyperthyroidism is a common condition called Graves’ Disease (named after an Irish Professor of Medicine, Robert James Graves). In this, the whole of the thyroid gland becomes active and enlarged due to an autoimmune mechanism. This is when the body produces antibodies against its own body organs or tissues. Other causes include an active nodule within the thyroid gland (toxic nodular goitre), temporary inflammation of the gland (thyroiditis) or rarely from disease elsewhere (eg pituitary hyperthyroidism, molar hyperthyroidism).

Is this a dangerous condition ?

Well, yes and no. If untreated and undetected, it can be life-threatening if the person undergoes any form of surgery. If unchecked, it can affect the heart, leading to heart failure and the bones resulting in bone thinning or osteoporosis. But most of the while, it causes very distressing symptoms to the person and loved ones around, which is entirely avoidable as this condition can easily be treated and even cured.

What are these symptoms ?

Though often a young or middle aged woman, this condition can affect all ages and both sexes. A prominent enlarged thyroid gland (goitre) is usually, but not always evident. The person is usually thin and keeps losing weight despite a hearty appetite. There may be trembling of the fingers when the hands are held outstretched, a feeling of being hot and more sweaty than usual, mood and personality changes like being anxious, irritable and bad-tempered. There may also be difficulty sleeping (insomnia) and vivid dreams or nightmares.

A racing heart rate (palpitations) is not uncommon. The limb girdle muscles (shoulder and hip) are sometimes weaker, causing difficulty in climbing staircases, and tasks that involve lifting the arms above the head. In women, there may be delay of their menstrual periods and infertility. Occasionally, there may be a protracted problem with loose and frequent bowel movements and a problem with hair loss. Other less common problems are swelling of the ankles and itchiness of the skin. The eyes can also be affected resulting in bulging of the eyeballs (proptosis), double vision (diplopia) and excessive teariness and a gritty sensation in the eyes.

Another helpful clue is a family history of thyroid conditions. With this and any of the above symptoms, then, consult your doctor who can easily arrange for a blood test to confirm or allay your suspicions.

What can be done ?

There are generally 3 options available to most persons with hyperthyroidism. Depending on the cause of the overactive state, one or more of the options may be suitable for you. Your doctor would best be able to discuss them with you and advise you on the relative benefits and risks of each.

a. Medical treatment.

This is by far the most common method. The tablets (carbimazole, thyrozol or propylthiouracil) have to taken religiously, daily for at least one-and-a-half to two years. They are usually well tolerated and the most important side effect is a very small (less than ½ %) chance of a lowered white cell count. As such, patients on the tablets are warned to stop their tablets and see their doctor for a blood test if they develop a high fever or prolonged (more than 5 days) sore throat. In fact, the tablets are so safe, that this is the treatment of choice in pregnant women with hyperthyroidism. Other side effects are a drug rash (which is common to almost any drug taken) and hair loss (which may be due to the underlying thyroid condition itself).

b. Surgery.

This may be an option for those with large goitres which may be cosmetically unacceptable or causing pressure symptoms to the surrounding neck structures. Also this may be considered if medical treatment had been tried previously and deemed a failure for whatever reason. The risks are with any surgical procedure and anaesthesia. In addition, there are small risks of causing injury to the parathyroid glands which lie behind the thyroid gland and control calcium metabolism , and to an adjacent nerve that may lead to voice hoarseness.

Usually two-thirds of the thyroid gland is removed, leaving a remnant for normal thyroid function. If too much is removed, then underactivity (hypo-thyroidism) ensues.

c. Radioactive Iodine Treatment.

Iodine which is found in high quantities in seafood, in taken up avidly by the thyroid gland to produce the thyroid hormones. This form of treatment employs use of a radioactive tracer of iodine which is administered orally in a liquid preparation. Usually only one dose, but sometimes two is needed and is given in an outpatient setting in a facility that is equipped to handle storage and disposal of this material. This is usually the Department of Nuclear Medicine at the Singapore General Hospital.

It is simple, inexpensive and effective. There are 3 main drawbacks. Effects are usually only seen 2 to 3 months after the dose is administered. As part of its role to normalise thyroid function, it causes an underactive thyroid to develop over the years after treatment, necessitating simple hormone replacement thereafter. The last drawback is related to its radioactive nature - it cannot be given in pregnancy and pregnancy should not be planned for at least 6 months after radioactive iodine is given. This form of therapy is therefore not of choice if pregnancy is being actively planned in a woman.

Is there any food I should avoid ?

Generally, no. But in everything, moderation is the key word. Seafood should not be taken excessively as this is a rich source of iodine. Seaweed in Japanese sushi and “agar-agar” is also a rich source of iodine. Before radioactive iodine treatment, subjects are usually advised to abstain from seafood.