Dr Warren Lee, MBBS, M Med (Paeds), FRCP (London), FRCPCH (UK), FAMS

Most people think that people with thyroid conditions need to take more iodine-­‐containing foods, like seaweed soup, and that some of them have eyes that bulge out like goldfish. Others associate a thyroid condition with being mentally retarded. How often have you heard someone mention that they themselves, their friend or relative has a thyroid condition and then wonder if you can catch the disease from sharing food or shaking hands?

Answer: thyroid conditions are not infectious, so you cannot 'catch' a thyroid condition from sharing food or shaking hands... or kissing.

The thyroid gland is a small butterfly-­‐shaped gland wrapped around the windpipe (trachea). In most people, it is barely visible and palpable just below the thyroid cartilage and weighs only about 10 to 20g.

It produces thyroxine, a hormone (chemical messenger) that helps the body to regulate our weight, our body temperature, the growth of our children and has an impact the process of puberty, menstrual cycles, bone mineral density, cholesterol levels, mood, 'energy levels' and if not present in sufficient amounts in newborns or infants has the potential to cause lifelong mental retardation.

If the thyroid gland is enlarged, it is called a goitre. However, not everyone with a thyroid condition has a goitre, and not everyone with a goitre will need medication or surgery. Sometimes excessive fat in the neck region is mistaken as a goitre and, vice versa, a thyroid lump or goitre can be missed by the patient and the doctor.

Thyroid conditions can affect people of all ages, and babies can be affected while in the mother's womb. Whole populations used to be affected when there was insufficient iodine (necessary for the body to make thyroxine) in the food supply, but this is extremely rare in Singapore unless the person is on an unusual diet.

In Singapore, children are tested for hypothyroidism by means of a cord blood screening test at birth. However, no screening test can detect 100% of children affected with hypothyroidism. It is always about a balance between sensitivity (picking up as many cases as possible) versus specificity (not causing unnecessary alarm to parents of a child because of a false positive result). Hence, milder cases or those with delayed onset hypothyroidism in childhood could be picked up late. If the body produces the correct amount of thyroxine, the person is in the EUTHYROID state.

If the body produces too much thyroxine, the condition is called HYPERTHYROIDISM.

Common symptoms of hyperthyroidism include:
Palpitations (a sensation of a strongly beating heart)
Fast heartbeat, even while at rest
Heat intolerance (prefers a cold environment)
Nervousness
Insomnia (unable to sleep well)
Breathlessness
Increased bowel movements (this can seem like diarrhoea)
Light or absent menstrual periods
Fatigue (gets tired easily)
Trembling hands
Weight loss (unintended and unexplained weight loss)
Warm moist skin
Hair loss
Staring gaze
Exophthalmos (sometimes described as goldfish eyes)
If the body produces too little thyroxine, the condition is called HYPOTHYROIDISM.

Common symptoms of hypothyroidism include:
Fatigue (easily tired)
Weakness (a feeling of lack of strength to perform physical activities)
Weight gain or difficulty in losing weight
Coarse, dry hair,
Dry, rough, pale skin
Hair loss
Cold intolerance (the person prefers a warm environment and feels cold even when other people may feel just right or even warm)
Muscle cramps and frequent muscle aches Constipation
Depression ( with feelings of sadness, helplessness and hopelessness ) 
Irritability
Memory loss
Abnormal menstrual cycles
Decreased libido (no interest in sex)

Thyroid conditions are not uncommon. Recent studies in the USA and Europe suggest that 5 to 10% of individuals in a community may have an underactive thyroid gland and about 10% of individuals with high cholesterol levels may have low thyroid levels as a cause. The symptoms vary between individuals. Some people have almost no symptoms (ie they do not notice) but they may still suffer the effects of an abnormal thyroid hormone level in their bodies.

About one child in every 4000 is born with a severely underactive thyroid gland, but many more children will have some form of underactive thyroid condition in childhood. Since 1987, Singapore has had a newborn thyroid screening programme that helps identify infants at risk of hypothyroidism. It is very successful, but some children may be missed, because screening programmes are meant to diagnose most but not necessarily everyone with a thyroid problem. Children with hypothyroidism can develop normally if treatment is started early, say within two to four weeks after birth.

Congenital hypothyroidism (being born with low thyroid hormone) can be caused by being born with no thyroid gland (athyreosis), small and malformed gland (dysplastic gland) or a gland situated in the wrong site within the body (ectopic gland), or it can be caused by a disorder of thyroxine production (thyroid dyshormonogenesis ).

Hypothyroidism could also be caused by an autoimmune process called lymphocytic thyroiditis or Hashimoto's disease. People with Hashimoto's disease often have a relative with Grave's Disease , another autoimmune disease where the abnormal antibodies cause excessive production of thyroxine and hyperthyroidism. Rarely hypothyroidism can be caused by surgery, or radiotherapy or medications.

Hyperthyroidism is most often caused by Graves Disease ( a condition in which abnormal antibodies cause the thyroid gland to grow and produce excessive thyroid hormone ) but sometimes it can be caused by an out of control abnormal nodule which is doing its own thing.

Hypothyroidism and hyperthyroidism can also affect height growth, obesity, appetite, bone mineral density, temperament and learning ability in childhood. Thyroid cancer is rare but can be present as a nodule (lump) in the thyroid and the person can be euthyroid, hypothyroid or hyperthyroid. Blood tests, ultrasounds, technetium scans and sometimes biopsies are needed to help make the diagnosis.

The general principles of treatment of thyroid conditions are well established and may involve medication, surgery or radioactive iodine (a liquid medication) or radiotherapy (special radiation to burn off abnormal cells).

However, first we must recognise the problem, get the diagnosis right and then titrate (adjust) the medication to be just right for the individual. This process can be straightforward for some patients, but extremely complicated for others because of individual patient variation. Children and young people can also suffer from the conditions mentioned, and some others beside. Because children need to grow, develop puberty and eventually reach a normal adult height and weight and to be as intelligent as their genes would allow, it is very important to ensure that hypothyroidism and hyperthyroidism be treated properly.

Children with thyroid disorders need special care to ensure that they get the best outcome in terms of height growth, weight gain, intellectual development, bone development, appetite and puberty, not just to get normal numbers on the blood tests, so it is best to see a doctor experienced in treating childhood thyroid disease if you suspect your child has a thyroid problem.