There’s something a little bit different about Tasmania. Not just the landscape but the people as well.

Pathologist Dr Lawrie Bott, who practiced medicine in Tasmania for 10 years and who has convict ancestral roots there, has heard the jaded crack about two-headed Tasmanians many a time, but suggests the jibe may relate to the condition iodine deficiency, causing a neck swelling called a goitre.

Untreated iodine deficiency at that time could cause a goitre the size of “another head”. Iodine deficiency, which also causes hypothyroidism, was a common ailment due to some topographical features peculiar to the Apple Isle.

“Soil in the South East of Australia, including areas from South Australia, Victoria, New South Wales and Queensland, but particularly Tasmania, contains very low levels of iodine,” says Dr Bott.

“Iodine is needed to produce thyroid hormones that are vital for the growth & well-being of many organs in the body, particularly the brain. And that lack of iodine in the diet has historically led to hypothyroidism, a condition that can have serious health consequences, not just for the thyroid but for other parts of the body as well.”

A defectively functioning thyroid caused by iodine deficiency has several effects on the body, one of them being the production of large neck masses, or goitres, which enlarge in an effort to maintain the production of vital thyroid hormones. Countries throughout the world who have iodine deficient soils, as Australia does, also suffer high levels of thyroid disease.

As a consequence, inadequate thyroid hormone production results in the disease state known as iodine deficiency disorder. This disorder results mainly from geological rather than social and economic conditions. It cannot be eliminated by changing dietary habits or by eating specific kinds of foods grown in the same area.

Thyroid disease is not an historic anomaly, it’s a condition that remains an issue today. Around 850,000 Australians will suffer a thyroid disease of some kind during their lifetime, including one in eight women, with 60,000 new cases per year. A study in those older than 49 showed thyroid disease in approximately 14% of people, either known or unknown.

Not all thyroid disease is caused by iodine deficiency, much is also caused by autoantibodies (e.g. Graves’ Disease and Hashimoto’s Disease) where the thyroid gland is attached by the body itself. Thyroid cancer also occurs but is relatively rare in Australia.

A history of iodine supplementation

Given the low levels of iodine in our food supply these days, it is recommended that supplementary iodine be consumed, particularly by pregnant women to ensure the normal development of the brain of the developing baby.

Dr Bott says that the lack of iodine in the Australian diet became so significant a health issue that in the 1950s a public health campaign pushed for the addition of iodine to salt and bread. In 1968, Tasmania established a thyroid advisory committee to address the problem.

Since the 1950s a lot has changed, not always for the better.

“Milk producers used to clean their vats with iodine, making milk an important source of the mineral, but that changed when they replaced iodine in favour of chlorine as the cleaning agent.

Research in Tasmania in the 1990s again showed deficiency in children and the state government negotiated with bakers to add iodised salt in all bread made in the state from 2001. In 2009 this action was put into legislation nationally. However, with the uptake of low carbohydrate diets, getting sufficient amounts of iodine is still an issue with advocates calling for it to be added to other foodstuffs.  

“Iodised salt is also a potential source of iodine, however with low salt diets and the fact that much of the produce on supermarket shelves today is not iodised is an issue. Although we are often eating more salt than we should, a lot of it doesn’t have the health benefits of iodised salt,” said Dr Bott.


Symptoms of hypothyroidism can manifest in a feeling of “slowing down”, including lethargy, feeling cold, hair loss or dryness, brittle nails, constipation, and high cholesterol.

Symptoms of hyperthyroidism are the opposite and the body is “revved up”, with symptoms including agitation, rapid pulse and weight loss.

Thyroid Function Tests

The only way to identify thyroid disease is through a pathology test.

Thyroid Function Tests can tell if your thyroid gland is functioning normally or is overactive (hyperthyroidism) or underactive (hypothyroidism).

Thyroid Function Tests include

  1. TSH (Thyroid Stimulating Hormone) which is produced by the pituitary gland in the brain and stimulates the thyroid gland and
  2. Thyroid Hormones – Thyroxine (T4) and Triiodothyronine (T3)

The Royal College of Pathologists of Australasia advises that all pregnant women should have their thyroid status checked as part of an antenatal screen.

If you are concerned about your thyroid a pathology test can be conducted at the recommendation of your GP.