Thyroid cancer is a weird one. The cause of this cancer is generally described as “unknown” and it has been on an unexplained upward swing in Australia since 1982.
In that time, the prevalence of thyroid cancer has gone from a few hundred cases to some thousands.
There’s growing evidence that weight gain, a higher Body Mass Index (BMI) and waist circumference could explain the steady increase of thyroid cancer cases.
In 1980, about 60 per cent of Australian adults had a healthy weight; today this has almost halved to about 35 per cent, according to an explainer from The Conversation.
In 1980, only 10 per cent of adults were obese
According to the Australian Institute of Health and Welfare, the prevalence of overweight and obesity among Australians aged 18 and over increased from 57 per cent in 1995 to 67 per cent in 2017-18.
The main driver was an increase in obesity, from one in five (19 per cent) in 1995 to one in three (31 per cent) in 2017-18.
In 2016, the World Health Organisation’s International Agency for Research on Cancer identified the link between thyroid cancer (among others) and obesity.
So, what is the thyroid?
The thyroid is a butterfly-shaped gland below the larynx (Adam’s apple), and comprises two lobes that lie on either side of the windpipe.
It secretes hormones that regulate various metabolic processes and growth.
Long-standing risk factors of thyroid cancer include a family history of goitre, exposure to high levels of radiation, and certain hereditary syndromes.
Goitre is an abnormal growth on the thyroid caused by an iodine deficiency or inflammation.
The most common types of thyroid cancer — papillary and follicular cancers — have a more than 98 per cent cure rate if they’re caught and treated at an early stage.
Data scientist predicts prevalence
In 1982, according to Cancer Australia, there were 361 new cases of thyroid cancer. In 2017, there were 3154.
Over the same period, the incidence rate increased from 2.7 cases per 100,000 persons (in 1982) to 12 cases per 100,000 in 2017.
A world-first study, led by Dr Maarit Laaksonen, a data scientist from the UNSW’s School of Mathematics and Statistics, found that one in five future thyroid cancers in Australia is “attributable to current levels of overweight and obesity”.
As a result, overweight and obesity “will be associated with 10,000 thyroid cancers in the next decade”.
Thyroid cancer is one of the few cancers that is two to three times as common in women as in men, but Dr Laaksonen says “the study found that the future thyroid cancer burden attributable to overweight/obese is higher for men compared with women”.
“It is still not well understood what causes the sex difference in overweight (and) obesity-related thyroid cancer risk,” Dr Laaksonen said, in a prepared statement.
“But our findings add evidence to the urgent need to halt and reverse the current global trend in weight gain, especially obesity and especially in men.”
The study findings were based on seven Australian cohort studies involving 370,000 participants, which enabled the evaluation of less common cancers such as thyroid cancer.
Dr Laaksonen is now planning a study on the preventable burden of stomach and oesophageal cancers, and a summary paper on preventable cancer burden in Australia across all cancers.