Thyroid conditions

What are thyroid conditions?

The thyroid is the largest endocrine gland in the body and it releases the hormone thyroxine into the blood. The main function of this hormone is to regulate the metabolic rate of the body. In addition, the hormones are needed to maintain the normal functioning of the brain. A thyroid gland can produce too much or too little hormone.

What are the complaints associated with a thyroid condition?

When the thyroid gland produces too much hormone, the metabolic rate increases. This is known as 'hyperthyroidism'. Possible symptoms are hot hands, sweating, weight loss, a rapid pulse rate and restlessness/agitation. The picture with hypothyroidism is the opposite. The thyroid gland does not produce enough hormone, making the metabolic rate too slow. The possible symptoms are cold feet, dry skin, a slow pulse rate, an increase in body weight, constipation and fatigue.

People with intellectual disabilities sometimes find it impossible to communicate these symptoms. The people around them may then notice only a change in behaviour.

How common are thyroid conditions in the general population?

The prevalence rates in the general population are 0.8% for hyperthyroidism and 2.4% for hypothyroidism. The total prevalence rate is therefore 3.2%. Both conditions are five times more common in women than in men and the prevalence rates increase with age. ⁹⁴

How common are thyroid conditions in people with intellectual disabilities?

In the Australian study conducted by Beange looking at 202 people with intellectual disabilities, blood tests revealed a prevalence rate of 12% for thyroid disease. ⁹⁵

A Dutch research of 946 people with intellectual disabilities without known thyroid disease (people who had already been treated for thyroid disease were therefore excluded) found a prevalence rate of 5.2% for previously undetected hypothyroidism and 2.8% for hyperthyroidism. The use of anti-epileptics affects thyroid function. ⁴⁶⁹
The European POMONA questionnaire survey looked at a random sample of 1269 adults with intellectual disabilities and found that 8% had thyroid conditions. ⁹⁶

Research has concentrated primarily on thyroid conditions in people with Down syndrome. In a US study of 1371 adults with intellectual disabilities, hypothyroidism was seen in 15% of all those studied with Down syndrome. ⁹⁷

The lifetime prevalence of hypothyroidism in people with Down syndrome is 25 to 30%. ⁹⁸

A major study in Spain of 1832 people with Down syndrome found a lifetime prevalence of hyperthyroidism of 0.65%. ⁹⁹

In addition to Down syndrome, there are other syndromes associated with a higher prevalence of thyroid conditions, such as Turner syndrome and congenital rubella syndrome. ^{98 470}