Working Long Hours Can Cause Underactive Thyroid Disease

London: Workaholics are more likely to have an underactive thyroid, known as hypothyroidism, according to a new study. Hypothyroidism was twice as common in people working more than 53 hours a week, compared with those working 36 to 42 hours a week the equivalent of a full-time 9-5 profession. An underactive thyroid has been linked to several health concerns, including heart disease and diabetes.

Hormones produced by the thyroid are crucial in controlling heart function, digestion muscle control, brain development, and bone maintenance. The researchers are unsure what it is about long working hours that could lead to the condition and hope further research can shed light on the correlation.

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‘Overwork is a prevalent problem threatening the health and safety of workers worldwide,’ said principal investigator Young Ki Lee at the National Cancer Center in Goyang-si, South Korea. ‘To our knowledge, this study is the first to show that long working hours are associated with hypothyroidism.’

Researchers found a higher risk of hypothyroidism in people who worked long hours regardless of their socioeconomic status. This is despite the fact that the disorder affects more women than men. The study results – published in Journal of the Endocrine Society – were due to be published at the Endocrine Society’s annual ENDO meeting in San Francisco this week

There are likely multiple factors linking long working hours and hypothyroidism that have not yet been studied in-depth, Professor Lee said. ‘Long working hours contribute to psychological stress, and rat models have shown that social, as well as physical chronic stress, reduced thyroid hormone levels,’ he said.

‘Overwork-related unhealthy metabolic conditions and physical inactivity may be another cause of hypothyroidism. Subclinical hypothyroidism is prevalent among patients with obesity.’ Because South Korea passed a law in 2018 that reduced the maximum number of working hours from 68 to 52 per week, a fall in hypothyroidism cases could be an important indicator in future studies.

‘If long working hours really cause hypothyroidism, the prevalence of hypothyroidism in Korea might decrease slightly as the working hours decrease,’ Lee said.


Hypothyroidism (underactive thyroid) is a condition in which your thyroid gland doesn’t produce enough of certain crucial hormones. Over time, untreated hypothyroidism can cause a number of health problems, such as obesity, joint pain, infertility, and heart disease.

Early symptoms of hypothyroidism can be fatigue and weight gain. But as the metabolism continues to slow, patients may develop more-obvious problems. These can include constipation, dry skin, weight gain, puffy face, muscle weakness, elevated blood cholesterol level, and pain, stiffness, or swelling in joints.

Most cases of underactive thyroid are caused by the immune system attacking the thyroid gland and damaging it, or by damage that occurs as a result of treatments for thyroid cancer or an overactive thyroid. The thyroid gland is an endocrine gland in your neck that makes two hormones that are secreted into the blood – thyroxine (T4) and triiodothyronine (T3)