Thyroid Gland

A few figures

  • LesThyroid disease affects over 15 % of the French population.
  • Thyroid nodules are to be found in 50% of women over 50and are 2 -3 times more frequent in women than in men.
  • Nearly 5 % of them are cancerous.
  • About 4,000 new cases of thyroid cancer are diagnosed in France each year and this number is constantly increasing at about the rate of 6 % a year.

The thyroide gland and how it works

The thyroid, situated below the larynx in the middle of the neck, is a butterfly-shaped gland formed by 2 lobes sitting across the windpipe one on either side. Its role is to produce hormones (endocrinal gland) that are released into the bloodstream to regulate the functioning of numerous organs.

Behind the thyroid there are 4 small, very fragile glands, the parathyroids that regulate the levels of calcium in the blood. At the back of the thyroid, there are 2 tiny nerves, one on either side, that are responsible for vocal cord movement and any injury to these nerves can, in certain cases lead to voice change.

Hormone-production control

The reason thyroid hormones have an effect on the system as a whole is due to their stimulation of cell activity. Among other functions, they regulate heartrate, weight, temperature, sleep and irritability. At every age in life, they are essential to the proper functioning of numerous vital organs.

T3, T4, TSH

La glande thyroïde

Among the hormones produced by the thyroid, the 2 main ones are T3 (triodothyrine) and T4 (thyroxine) and their synthesis is regulated by 2 structures situated in the brain, the hypothalamus and thepituary gland.

The hypothalamus acts on the pituary gland which itself acts on the thyroid by secreting the TSH that has the primordial function of regulating the secretion rate of the thyroid hormones T3 and T4. This process allows a very finely-tuned regulation of the thyroid hormone levels in the blood.

If the body is to function properly, a proper dosage is essential.

Cancer of the thyroid

About 5 % of thyroid tumours are cancerous.
Cancer of the thyroid represents about 1 % of the cancers that appear in the general population. It remains relatively rare and under 4,000 people get it per year.

The number of those who have this cancer is constantly rising

Risk factors for cancer of the thyroid.

Only the risk factors for cancer of the thyroid are known. Its causes still remain unknown. It occurs more frequently when iodine intake is very low or in those patients who have undergone medical or accidental radiation.

Cancer of the thyroid has been on the increase in France and most countries in the West since the 1970s.
According to the French data supplied by the INVS, the number of male thryroid cancer cases has risen from 325 in 1980 to 1599 in 2005. In women, the number has risen from 1027 in 1980 to 5073 in 2005. Gratifyingly, these rises are not echoed in the death rate. On the contrary, the number of deaths has dropped by about 400 per year.

This cancer occurs in more women than men and it is diagnosed most frequently between the ages of 30-50.

According to INVS experts, this rise in occurence is essentially due to better methods of early diagnosis without mentioning increasing application of surgical practice rather than the Tchernobyl nuclear accident that is often suspected by the general public of being responsible.

Discovering a nodule

The discovery of a nodule almost always leads to a closer examination of the thyroid in order to ascertain whether or not cancer is present.
This nodule can be discovered in various ways.

  • The presence of a ‘lump’ in the lower half of the neck that moves with swallowing without any discomfort being felt.
  • More and more often by the accidental discovery of a small nodule when a medical imaging examination (Doppler, ultrasound of the neck) is being carried out for some other reason.
  • Sometimes by the presence of a neck ganglion, an increase in size of a known goiter, difficulty in swallowing, a change in the voice, a persistent unexplained cough.

Identifying cancer of the thyroid

Diagnosis is made thanks to the results of the different examinations and tests described above, particularly cytopunction.

Thyroid cancer treatment

Undertaken in successive stages.

Surgery
The surgeon performs a complete thyroidectomy that is to say , total removal of the thyroid gland. This is the surest way of avoiding any extension of the tumour, facilitating the complementary medical treatment and ulterior follow-up.

After this surgery, Thyroxine (T4) must be taken to compensate for thyroid absence.

Using iodine 131

Allows not only the elimination of any possible normal thyroid residue but above all any remaining cancerous thyroid tissues.

If the risk of reoccurrence after total removal is very low, this treatment is not carried out.

Iodine 131 is administered after stimulation of the TSH obtained either after prolonged hypothyroiditis or by injections of biotechnological <>. A rise in TSH levels is thus obtained without having to interrupt the Levothyrox treatment. The iodine is administered by intra- muscular injection on 2 consecutive days followed by treatment with radioactive iodine on the 3rd day.

Prognosis

If detected early, this cancer has a close to 100 % cure rate. However recovery depends on certain other parameters:

  • In the adult, the risk of the cancer returning increases with the patient’s age and the tumour’s extension. With children, reoccurrence is relatively frequent.
  • Life expectancy depends on the patient’s age and if the cancerous cells have spread. For instance, risk of death is greater for the over-65s

Screening

is important in the following cases:

  • When thyroid cancer runs in the family.
  • After radiation treatment for breast cancer - ultrasound examination of the thyroid carried out at the same time as regular control mammography is advisable.
  • In iodine-poor areas such as the east of France.

Livret d’information patients « Le cancer de la thyroïde » créé par le Pr. Martin Schlumberger, chef du Service de Médecine Nucléaire à l’Institut Gustave Roussy (IGR), à Villejuif. Belot A, Grosdaude P, Bossard N, Jougla E, Benhamou E, Delafosse P, et al. Cancer incidence and mortality in France over the period 1980-2005. Rev Epidemiol Sante PUblique 2008; 56:159-75
Eur J Cancer, 2002 Sep ; 38(13) :1762-8.

Institut National de Veille Sanitaire.

Sassolas G, Hafdi6Nejjari Z, Remontet L, Bossard N, Belot A, Berger-Dutrieux N, et al. Thyroid cancer : Is the incidence rise abating ? Eur J Endocrinol. 2009 ; 160 :71-9.