Thyroid

General information

The thyroid is located in the anterior region of the neck; it weighs about 20gr and is composed of two lobes (right and left) that are connected by the ‘isthmus’.
The thyroid gland produces three hormones 1) thyroxine or tetraiodothyronine (T4) and 2) triiodothyronine (Τ3) which regulate the metabolism of all tissues, and 3) calcitonin.  The composition and secretion of the thyroid hormones is regulated by thyroid-stimulating hormone (TSH), or thyrotropin, which is produced in the pituitary, an endocrine gland located in the brain. TSH in its turn is dependent on the secretion of thyrotropin-releasing hormone (TRH) that is produced by the hypothalamus also located in the brain and which is the body’s metabolism centre.  Iodine, which is essential for the synthesis of thyroid hormones, is concentrated in the thyroid.

A) Causes of thyroid diseases

The main causes of thyroid diseases identified so far are autoimmune, stress, diet, radiation, radioactivity, some medications.

B) Diseases of the thyroid gland

It must be stressed that the symptoms listed below are provided only for general information and are in no way an absolute diagnostic guide.  Should a patient note that he has any of these symptoms, he needs to promptly contact a specialized endocrinologist who will pinpoint their cause. The endocrinologist will then be able to accurately diagnose the symptoms and evaluate the patient’s blood hormones levels as from the earliest stages when the symptoms are still mild and the blood hormones are as yet at borderline levels. Any deterioration of the symptoms of the disease is thus avoided from early on.

1) Congenital hypothyroidism at birth

2) Hyperthyroidism / Exophthalmos
Hyperthyroidism, also known as overactive thyroid, is a condition in which the thyroid produces and secretes excessive amounts of thyroid hormones, this resulting in increased metabolism.  The symptoms include the following:

  • sudden weight loss
  • hypersensitivity to heat
  • weakness, fatigue
  • sleeplessness
  • tachycardia (rapid heart beat), high blood pressure, atrial fibrillation of the heart
  • nervousness, anxiety, irritability, hyperactivity
  • increased sweating
  • protrusion of the eyeballs (Graves’ ophthalmopathy), this measured by the Hertel exophthalmometer
  • diarrhoea
  • enlarged thyroid gland (goitre)
  • skin problems
  • disordered menstrual patterns in women

Treatment of hyperthyroidism includes antithyroid medication, radioactive iodine and extraction of the thyroid gland. The choice of the most appropriate treatment is made by the endocrinologist and differs from patient to patient.

Abnormal protrusion of the eyeballs, or proptosis (bulging) of the eye(s), otherwise known as exophthalmos, that is often caused by Graves’ ophthalmopathy or, more rarely by hypothyroidism, requires regulation of the thyroid hormones.  However, it may also appear several years after the illness and when the thyroid hormones have returned to normal levels.  The precise treatment of the main symptoms related to the eye, such as tearing / lacrimation, painful eyes, the feeling of having a foreign body in the eye, loss of colour vision (diagnosis via special testing), red eyes, double vision, swelling around the eyes, will be decided by the endocrinologist and always in collaboration with the ophthalmologist. The Hertel exophthalmometer is used to monitor the course of the disease.

3) Hypothyroidism
Hypothyroidism is another disorder of the thyroid gland that is characterized by underactivity of the thyroid and low production of thyroid hormones, which results in decreased metabolism.  Symptoms include the following:

  • unexplained weight gain
  • hypersensitivity to cold
  • muscle weakness, chronic fatigue
  • constipation
  • dry skin
  • skin disorders
  • disordered menstrual patterns in women
  • enlarged thyroid gland (goitre)
  • nervousness, irritability, restlessness
  • disrupted heart rate
  • vertigo, headaches
  • depression, mood swings
  • swelling around the eyes

4) Thyroiditis
This includes a group of disorders that cause inflammation of the thyroid. They either mark an early stage of the main disease or are transient derangements of thyroid function that are treatable with appropriate care and monitoring.

5) Goitre – Thyroid nodules
An important clinical finding of the morphology of the thyroid is if it is swollen or enlarged, i.e. if there is a goitre, which however does not always occur when there is a disease of the gland (e.g. hyper- or hypothyroidism, iodine deficiency). Any significant swellings can become evident as the gland follows the movements of swallowing and from its ‘bobbing’ along with the Adam’s apple. Each swelling is clinically referred to as goitre. A goitre requires treatment only if it causes symptoms.  Treatments include, depending on the cause, thyroid hormone replacement pills, radioactive iodine, thyroidectomy to remove all or part of the gland.
Thyroid nodules comprise an autonomous growth or lump in the thyroid. They may be single (a solitary nodule) or multiple. They can be compact cysts or mixed cystic.  They have a tendency to grow and spread; however, it is not possible to determine beforehand which will do so and how much. They must therefore be followed via ultrasound scan as well as with blood tests, since some of these may produce thyroid hormones.
The likelihood of a nodule being malignant is about 10-20% and depends on the patient’s history. The most effective and accurate manner of following the morphology of a nodule is by ultrasound of the thyroid. As mentioned, follow-up of nodules must be carried out via ultrasonography to monitor their course of growth as regards size, shape, ultrasonographic features such as echogenicity and blood flow pattern.  This is because there are no reliable ultrasonographic features (thyroid nodules blood flow by Doppler sonography, hardness by elastrograhy, reflex pattern, borders, change of size) or reliable cancer markers in the blood that, of themselves, would be able to identify the probability of a nodule being malignant. The presence of certain suspicious ultrasonographic features in combination with the clinical data and the medical history of the patient are that which will enable the endocrinologist to choose the most reliable test (besides the histological one) available to determine whether there is malignancy:  this is fine-needle aspiration (FNA) biopsy of the thyroid, thanks to which unnecessary surgery can be avoided.  Not all nodules are candidates for FNA.
Treatment of thyroid nodules is carried out via thyroxine suppressive therapy and radioactive iodine or else the thyroid gland is removed.  Therapy with suppressive doses of thyroxine is not effective or beneficial for all nodules.  In first-time diagnosed nodules that measure over 10 centimetres, the first thing is to ensure that it is a benign nodule so that a needless therapy is not carried out on a nodule that is potentially malignant.  There are a large number of nodules that do not respond to the thyroxine suppressive dose. Meanwhile, there are also patients who experience side effects from the high doses on their cardiovascular system and/or on their bones or who undergo a deterioration of a psychological illness. The endocrinologist is called upon to determine whether a patient is a suitable candidate for therapy with thyroxine as well as to assess the results during the course of treatment.

6) Cancer of the thyroid gland
There are four histological types of thyroid cancer. After total removal of the thyroid gland and according to the histology findings, it is decided whether radioactive iodine will be administered.
Monitoring of the course of the disease (recurrence of the disease or metastases) is conducted by the endocrinologist and during the early stages frequent doctor visits and checks are required.

C) Blood monitoring, measurements

While some thyroid hormones circulate in the body in conjunction with protein (total T4 and total T3), others circulate free thus being termed the free form (free T4, freeT3).  In accordance with the patient and his disease, the endocrinologist will choose the form of hormone that will be measured which will yield the best information for diagnosis. Although thyroid antibodies (thyroglobin antibodies [anti-TG], antithyroid peroxidase [anti-TPO]) are those that are measurable in the blood and show up the cause of numerous autoimmune thyroid diseases, there are no treatments to reduce their increased levels and thus it is not always necessary to measure them during therapy.

D) Thyroid ultrasound

Ultrasound of the thyroid gland is one of the most reliable and accurate means of following the morphology of the thyroid. It is a bloodless non-interventional method of short duration and is relatively cheap.

E) Fine-needle aspiration biopsy of the thyroid

This is by far the most accurate test (accuracy rate 90-95%) for evaluating thyroid nodules and ruling out the possibility of a thyroid malignancy without the need for surgery. Its results are evaluated by the endocrinologist who decides on any further diagnostic or therapeutic stages (histological).  In a few cases, a second biopsy is required.  The great advantage of this is that, apart from the heightened diagnostic value achieved, the patient in most cases will safely avoid surgery.

F) Scintigraphy of the thyroid with technetium

Since the advent of FNA, the older use of scintigraphy of the thyroid for determination of the presence of a cancerous or non-cancerous nodule (‘cold’ or ‘hot’ nodule) is rarely used any more as 9 out of 10 nodules are cold and yet non-cancerous. Nowadays, scintigraphy is employed for investigation into the functioning of the thyroid (hyperthyroidism, thyroiditis).
|
|

Images
Goitre  (thyroid enlargement) in a patient
with thyroid eye disease:    before and after treatment		 Dysthyroid ophthalmopathy, right eye disease
Dermopathy of the tibia in a patient with thyroid disease Dysthyroid ophthalmopathy in a patient with
dysthyroid eye – Periorbital edema (“swollen eye”)
Vitiligo (discolouration) on the hand
of a patient with Graves’ disease		 Thyroid acropathy of the finger and
incipient destruction of the nail
Dysthyroid ophthalmopathy in patients with thyroid disease (“red eyes”)
Measurement of exophthalmos (protruding eye)
with Hertel exophthalmometer		 Fine-needle aspiration
biopsy of the thyroid