Hyperthyroidism: symptoms and causes

By Cristiano Antonino On Nov 2, 2022

Hyperthyroidism is the condition in which the thyroid gland releases large amounts of thyroid hormones: thyroxine (T4) and triiodothyronine (T3)

These hormones are produced when the thyroid gland is stimulated in turn by another hormone, TSH (or thyroid-stimulating hormone), produced by the pituitary gland (pituitary gland) located in the brain.

Hyperthyroidism occurs when the thyroid gland functions more than it should.

Causes of hyperthyroidism

There are many causes of hyperthyroidism.

The most common cause is Basedow’s disease, an autoimmune disorder that, through the formation of antibodies against the TSH receptor, present on the thyroid gland, stimulates it to function more than it should; in this case, the thyroid gland often appears increased in size but without nodules and is often accompanied by eye disorders (burning, photophobia, exophthalmos) that give the picture of Basedow’s ophthalmopathy.

Hyperthyroidism, however, can also occur in toxic multinodular goiter; in this case, one or more nodules that have been present in the thyroid gland for years begin to function more than they should by producing excess thyroid hormones.

In the case of Plummer’s disease, on the other hand, only one nodule (and not many as in goitre) is present in the thyroid gland, which, producing large amounts of thyroid hormones, causes hyperthyroidism.

Less frequent, but not very rare, is hyperthyroidism due to an excess of iodine or in the context of autoimmune thyroiditis (Hashitoxicosis), in which damage to thyroid tissue due to the formation of antibodies against the thyroid (anti-thyreoperoxidase and anti-thyroglobulin) or infections results in the thyroid hormones produced by the thyroid gland being released into the circulation.

Lastly, there are much rarer causes of hyperthyroidism such as TSH-secreting pituitary adenoma and choriocarcinomas, which involve hyperstimulation of the thyroid gland through increased TSH.

Symptoms of hyperthyroidism

These conditions, along with other causes of thyrotoxicosis (taking drugs or substances containing thyroid hormones) share the same clinical manifestations.

The most frequent symptoms are nervousness, heart palpitation, sweating, intolerance to heat, muscle fatigue, diarrhoea and weight loss despite increased appetite.

Sexual disorders such as menstrual irregularities (in females) and premature ejaculation (in males) are often present.

These symptoms, especially in Basedow’s disease, may be accompanied by other eye symptoms such as burning, photophobia and exophthalmos (i.e. protrusion of the eyeballs).

Diagnosis of hyperthyroidism

Hyperthyroidism is diagnosed by testing, with a simple blood sample, free thyroid hormones (FT3 and FT4), which are very high, and TSH, which is usually low, in cases of primary hyperthyroidism (i.e. due to thyroid causes).

In order to identify what type of hyperthyroidism we are dealing with, it may also be useful to test for autoantibodies, which may be more or less altered. An ultrasound of the thyroid gland and, sometimes, thyroid scintigraphy are also essential to complete the diagnosis.

Therapy: how to treat hyperthyroidism

Once the cause of hyperthyroidism is identified, therapy is instituted. In all cases of hyperthyroidism, symptomatic drugs can be used to reduce the symptoms (beta-blockers); but depending on the type of hyperthyroidism, the most suitable therapy will be instituted.

The therapy may be pharmacological (involving the use of thyrostatic drugs that reduce thyroid activity), radiometabolic (involving the use of radioactive iodine) or, in some cases, surgical with the removal of part or all of the thyroid gland.

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