Hypothyroidism

Hypothyroidism
A Goitre is a Thing of Beauty

When earthquakes damaged the Fukushima Daiichi nuclear reactors in March 2011, a large quantity of radioactive caesium-137 and iodine-131 were released into the water supply. The Japanese government was accused of responding too slowly, and for not administering iodide prophylaxis to the exposed population.

Iodine-131 is readily taken up by the thyroid gland, and the radioactivity can destroy the gland. However, this uptake of radioactive iodine can be blocked by giving iodide orally, thereby preventing hypothyroidism.

The thyroid gland speeds up many metabolic reactions. A person with low thyroid hormone levels grows slowly, feels the cold more readily, thinks more slowly. If untreated, a hypothyroid person may become intellectually disabled. The thyroid gland in the neck may try to compensate for its low production by enlarging, and this is known as a goitre.

The link between iodine and the thyroid gland is interesting. Worldwide, the most common cause of goitres is iodine deficiency. And one of the commonest causes of preventable intellectual disability is iodine-deficient hypothyroidism.

Places far from the sea, like Switzerland, the Himalayas, the highlands of New Guinea, used to have a higher incidence of goitres. There are some gargoyles in Switzerland carved during the medieval era, depicting persons with goitres and donkey's ears. Presumably donkeys have a lower IQ than their relatives, the horses (I'm not so sure about smart asses).

In 1600 BC, the Chinese used burnt seaweed, which is rich in iodine, to treat goitres. Iodine was first introduced into our table salt 3½ thousand years later, in the 1920s.

The breast concentrates iodine so that breast milk contains increased iodine content. Hence nature has innately learnt to prevent iodine-deficient hypothyroidism.

A goitre can be found in both the underfunctioning as well as the overfunctioning thyroid gland. In the case of an overactive thyroid gland, also known as hyperthyroidism, the affected person can eat like a horse but fails to gain weight or might even lose weight, dislikes hot weather, is often sweaty, and the mind is overanxious, hyperactive, and he might suffer insomnia or sleepwalking.

A goitre used to be considered by men to be a thing of beauty for women to possess. Indeed there is a portrait of Queen Cleopatra (69-30 BC) showing her goitre. According to Plutarch, her intelligence far outweighed her looks. Presumably she had an overfunctioning thyroid gland.

What about behavioral problems? I am often referred children with attention deficit hyperactivity disorder to rule out hyperthyroidism as a cause of the behavioral problem. Rarely do I find abnormal thyroid function.

On the other hand, there are some people who suffer from depression and are found to have hypothyroidism. What is problematic is the person with depression who has a normal thyroid hormone, but a raised thyroid stimulating hormone (TSH).

The TSH is another hormone made in the pituitary gland located at the base of the brain, and is elevated when blood levels of thyroid hormone start to drop; it therefore stimulates the thyroid gland to make more thyroid hormone, bringing blood levels of thyroid hormone back to normal.

Raised TSH levels are often an early warning for looming hypothyroidism. Most pediatricians would probably start treatment with thyroid hormone replacement when they see a very high level of TSH, even in the presence of a normal level of thyroid hormone. However, when the level of TSH is only slightly raised, it is debatable whether or not to start treatment.

Treatment with thyroid hormone replacement seems to alleviate depression. We are still awaiting definitive evidence. Unfortunately in the interim, there may be rush to treating all patients suffering depression with thyroid hormone.