Toxic thyroid
A toxic thyroid nodule causes hyperthyroidism (an overactive thyroid). This occurs when a single nodule (or lump) grows on the thyroid gland causing it to become enlarged and produce excess thyroid hormones. If the increased hormone production is coming from a single nodule in the gland, this is called toxic adenoma. If there are many nodules causing the hyperthyroidism, this is referred to as multinodular goitre.
Causes a toxic thyroid nodule
The thyroid gland needs iodine to produce the thyroid hormones thyroxine and triiodothyronine. If iodine is lacking in the diet, the thyroid initially cannot produce enough thyroid hormones. Low levels of thyroid hormones cause the thyroid gland to grow as it works harder to absorb as much available iodine from the bloodstream as possible in order to make more thyroid hormones. The thyroid uses iodine to produce its hormones. Without enough iodine, the thyroid cannot perform its normal functions. Some people have greater risk factors for developing a multinodular goiter. Risk factors include:
- sex — women are more likely to develop nodules and thyroid disease
- age — older women are at higher risk of developing thyroid nodules
- a family history of multinodular goiter
- a history of an autoimmune thyroid condition, such as Hashimoto’s thyroiditis or Graves’ disease
- In some instances, a person may have no known cause for their multinodular goiter.
Signs and symptoms of toxic thyroid
The symptoms of a toxic thyroid nodule are a result of the high levels of thyroid hormones in the blood, increasing the rate at which the body is working. Similar to those of hyperthyroidism, these symptoms include:
- weight loss
- diarrhoea
- increased appetite
- flushing
- irritability
- tiredness
- palpitations (increased heart rate which can be felt by the patient)
- poor sleep
- increased sweating
- a tremor
- heat intolerance (feeling excessively hot )
Prevalence of toxic thyroid
Thyroid disorders are much more common in women than in men. Figures from the USA state that the incidence of toxic thyroid nodules accounts for 3–5% of patients with hyperthyroidism. Toxic nodules are more common in elderly people, particularly in areas of iodine deficiency.
Toxic thyroid detection methods
Blood test: A blood test is carried out to measure thyroid hormone levels and a full medical history should be taken.
Ultrasound: An ultrasound scan of the neck may be carried out to assess the thyroid nodule, and a tissue sample may be taken for analysis.
Computerised tomography (CT) scan: In a small number of cases, Rarely, a computerised tomography (CT) scan may also be performed to obtain a more detailed image of the gland.
Iodine uptake scan: A thyroid iodine uptake scan may also be performed. This is a test to measure how much iodine is taken up by the thyroid gland and gives an indication of whether the thyroid gland is under or overactive. In the case of a toxic nodule, you can see one area of increased uptake of iodine, with the rest of the gland suppressed.
Toxic thyroid treatment strategies
There are three main treatment options:
Radioiodine: is the most effective treatment to cure a toxic nodule (adenoma). It involves the patient taking either a capsule or liquid containing radioactive iodine. This can be carried out in the outpatient department. Iodine is used mostly by the thyroid gland so that all the radioiodine is concentrated in the gland and causes a gradual destruction of it. The iodine does not affect any other part of the body and is a safe treatment. However, there are temporary restrictions such as avoiding close contact with children and pregnant women in the first few weeks following treatment.
Surgery: may be carried out to remove excessive thyroid tissue and nodules, which will treat the hyperthyroidism. If the nodules are large, surgery will treat compressive symptoms of the enlarged thyroid such as breathing and swallowing difficulties. If a total thyroidectomy is carried out (to remove the whole thyroid gland), thyroid hormone replacement will need to be taken for life. Surgery is usually very effective, but a small number of patients develop recurrence of the nodules.
Medication: anti-thyroid drugs such as carbimazole are used to control the overactive thyroid symptoms, but these are not a cure, and if stopped, the patient will return to having hyperthyroidism. Carbimazole, which is taken as tablets, is mainly used either before surgery to control symptoms or in patients where other treatment options are not possible.
Complications of untreated toxic thyroid
If untreated, besides feeling poorly and unwell, the patient is also at risk of heart dysfunction or failure due to the increased heart rate and raised metabolic state. This irregular heart rate can result in strokes and dizziness. Long-standing toxic nodules can also affect the patient’s bones and cause osteoporosis, which results in weak bones that are more likely to fracture. The patient may also develop symptoms due to the enlarged thyroid gland such as difficulty with breathing or swallowing.
References
https://www.uclahealth.org/endocrine-center/toxic-nodular-goiter
https://www.yourhormones.info/endocrine-conditions/toxic-thyroid-nodule/
https://www.pennmedicine.org/for-patients-and-visitors/patient-information/conditions-treated-a-to-z/toxic-nodular-goiter
https://www.medicalnewstoday.com/articles/321790#outlook
