Autoimmune thyroid diseases are inflammatory diseases of autoimmune origin, in which the inflammation affecting the thyroid is primarily caused by an abnormal immune response of the body, which erroneously attacks and gradually destroys the thyroid gland.
Autoimmune thyroid diseases are particularly common in females since they affect approximately 2-4% of women and up to 1% of men worldwide, and their prevalence increases with age.
The two most common clinical forms are Hashimoto’s thyroiditis and Basedow’s disease (also known as Graves’ disease), but other types also exist, such as atrophic autoimmune thyroiditis, silent thyroiditis and post-partum thyroiditis.
Hashimoto’s thyroiditis is the most common thyroid condition and the most frequent cause of hypothyroidism. For reasons that are still not completely clear, the body produces autoantibodies (the autoantibodies found on tests are usually anti-thyroid peroxidase antibodies [TPO Ab] and anti-thyroglobulin antibodies [Tg Ab]), that attack the thyroid making it incapable of producing sufficient quantities of thyroid hormones. As a result of the decreased levels of thyroid hormones in the blood, the pituitary gland increases the production of thyroid-stimulating hormone (TSH), which in turn causes an increase in the volume of the thyroid gland, in the form of a goitre, a swelling that can be more or less evident depending on its size.
The symptoms caused by Hashimoto’s thyroiditis are those typical of hypothyroidism, such as weight gain, constipation, dry skin, irregular periods, depression and memory changes.
This is a rare variant of Hashimoto’s thyroiditis, in which the thyroid gland is severely atrophied (reduced) due to autoantibody attack, but in this case, there is no goitre. The disease is initially subtle and the patient may not experience any symptoms, even for several years, but it becomes evident when hypothyroidism sets in.
In this type of autoimmune thyroiditis the inflammation of the thyroid occurs without pain (hence its name). It is a particular form that tends to resolve spontaneously or following a short period of therapy. There is an initial phase of hyperthyroidism, in which the inflamed gland releases large quantities of thyroid hormones into the bloodstream and symptoms like anxiety, insomnia, palpitations and weight loss can ensue. During the second phase there may be a period of hypothyroidism, with the enlargement of the thyroid and the onset of the corresponding disorders, such as tiredness, weight gain, muscle weakness and slowed heart rate. Lastly, after about 12-18 months, the thyroid starts working normally again.
Post-partum thyroiditis presents within a year of childbirth and affects 5% to 8% of women. It is a transient form of thyroiditis, but consists of three separate phases: A first phase in which the inflamed thyroid releases into the bloodstream large quantities of thyroid hormones, leading to a state of hyperthyroidism that can last 1-2 months, during which symptoms such as anxiety, insomnia, irritability and weight loss occur. A second phase in which there may be a period of hypothyroidism with symptoms such as tiredness, constipation, depression, weight gain, muscle weakness and dry skin. Lastly, a third phase, in which the thyroid starts working normally again, usually 12-18 months after the onset of the symptoms. Although most women recover completely within a year, a high percentage of those who have experienced the hypothyroidism phase tend to develop permanent hypothyroidism, even after an initial remission phase. In 70% of cases, post-partum thyroiditis recurs with subsequent pregnancies.
Basedow’s disease (or Graves’ disease) is a disease that primarily affects women, usually between 30 and 50 years of age, and is the most common cause of hyperthyroidism (in which there is an excessive production of thyroid hormones). It is due to abnormal production by the immune system of antibodies that perceive the thyroid as foreign and attack it, thus hindering its normal activity and stimulating an uncontrolled production of thyroid hormones.
As thyroid hormones are involved in the function of many organs, the symptoms can include weight loss, anxiety, irritability and sleep disorders, sensitivity to heat and increased sweating, intestinal problems, thickening and reddening of the skin, shortness of breath, tachycardia, palpitations and enlargement of the thyroid (goitre).
Up to half of all people with Graves’ disease can develop ocular symptoms: eye pressure or pain, eyelid swelling or retraction, red, irritated eyes upon waking, sensitivity to light and double vision (diplopia). This condition is known as Graves’ ophthalmopathy or orbitopathy.
The term thyroid nodule refers to a small solid or fluid-filled growth that forms inside the thyroid and that, in the vast majority of cases (90-95%), is benign (non-cancerous). It is a very common condition that occurs in 50-65% of healthy individuals, it is more common in women than in men and mainly affects the elderly and people living in areas of iodine deficiency. They are rare in children.
Although thyroid nodules usually do not cause symptoms and they are often detected incidentally during a medical examination, in some cases they can grow and become visible as round swellings at the base of the neck or, when they get larger, they can cause symptoms like breathing difficulties or sensations of swallowing difficulties, pain in the neck, upper jaw or ear, or throat discomfort.
Thyroid nodules can be:
For diagnosis, a physical examination of the neck and the patient’s medical history are fundamentally important. In addition, in order to examine the nodule, the doctor will order certain investigations, such as an ultrasound scan or, when malignancy is suspected, other imaging procedures. In suspect cases, a fine-needle biopsy will also be carried out in order to collect and analyse a sample of cells from the nodule.
If malignancy is confirmed, the nodule or, if necessary, the entire gland will be surgically removed, whereas if it is benign, and there are no symptoms, it will simply be monitored over time with regular check-ups.