Which function does the thyroid have?
The thyroid gland (in latin: glandula thyroidea) is a hormone producing organ in the shape of a butterfly, which is located in the neck, in front of the trachea and the thyroid cartilage. The regular femal thyroid reaches a total capacity of 18 ml and the male one up on to 25ml. The thyroid saves (stores) iodine and produces the iodine containing thyroid hormones Thyroxine (T4) and Triiodthyronine (T3), which have a major influence on the metabolism and the growth of the cells. Furthermore it produces the hormone calcitonin, a hormone which is in charge of the mount of calcium and phosphate in the bones and counters advancing osteoporosis. A hyperfunction of the thyroid is called hyperthyroidism and a hypofunction is called hypothyroidism. A special case of hyperthyroidism is Graves’ disease, where thyroid antibodies have a stimulating influence on the thyroid.
What is a goiter?
A goiter is an amplification of the thyroid, which imposes pressure on close-by organs like the trachea and the gullet, and causes complains. The most common source of a goiter is a lack of iodine. The body recognizes the deficient supply of iodine, the TSH (thyroid stimulating hormone) is increasingly distributed and thereby stimulates the thyroid to growth. About 15 to 30% of the adult population in central Europe suffer of a goiter. Within the last years it was possible to prove, that even with sufficient supply of iodine, but due to inborn, predisposing factors a goiter can be developed. Hence the lack of iodine is a secondary stimulating factor. The enlargement of the thyroid can be caused by the development of nodules (struma nodosa). In case of regular hormone production the goiter is called euthyroid.
What does a thyroid nodule mean?
Most thyroid nodules are benign. Most of the times they are cysts. 25% of the population do have thyroid nodules, but only 0,1% of the thyroid nodules are malignant. In the matter of the identification of the knots, the following examinations can be done: ultrasound (sonography) with colour duplex, radionuclide scanning, FNA (fine needle aspiration biopsy), serum analysis with calcitonin and thyreoglobulin levels. Depending on the examinations results, a therapy will be initiated or check-ups will be recommended. In order to eliminate a carcinoma, other signs like tendency of growth, proof of enlarged lymphnodes or hoarseness, will be considered.
For example, in the 99mTc scintigraphy less storing nodules, so called cold nodules, are up to 4% malignant. In suspicion of carcinoma a surgical therapy will be initiated. A fine needel punction of a nodule, controlled by ultrasound, gives in only 2% an incorrect negative result.
What kinds of thyroid carcinomas are known?
The malignant neoplasm of the thyroid appears in 4 cases out of 100 000 inhabits and is the third frequently tumor with women under the 40th year of age. The influence of ionized rays was proven. For example after the Tschernobyl-nuclear accident, 1500 Children suffered from thyroid-carcinomas in the nearby areas. Within the last years a rising tendency of illness has been recorded.
The thyroid malignancies are divided into the following forms: follicular carcinoma (FTC) (20-40%), papillary carcinoma (50-70%), anaplastic carcinoma (less than 5%), medullary carcinoma (about 5%). Medullary carcinoma (MCT) occurs in 15% as a inborn form (MEN- multiple endocrine neoplasia). The 10 years survival rates are: papillary > 90%, FTC >75%, medullary about 50%.
What is a thyreoditis?
Thyreoditis is a case of a inflammation of the thyroid, which can be divided into the following subcategories:
- Acute thyreoiditis: very seldom, caused by bacteria and funguses
- Hashimoto (chronic thyreoiditis): Distortion through autoimmune processes. An increased occurrence of papillary carcinomas was seen in the thyroid nodules.
- Subacute thyreoiditis (de Quervain) often appears subsequently to a virus based infection of the respiratory tract and abates spontaneously after few weeks, in most of the times.
- Riedel thyreoiditis appears very seldom.
Which forms of therapy do exist?
When there is no suspicion of a carcinoma, a medication or radioiodine based therapy can be initiated. The LISA study constrained, that after a year of a combined treatment with iodide an l-thyroxin the goiter-volume was reduced about 10% and the nodules sizes reduced about 21%. That means that this kind of therapy is more effective than a treatment based completely on iodine or LT4. The I-131 radio –iodine-therapy can be used as well in case of an non efficient medication therapy of the hyperthyreosis or goiter, and as an addition to an operation of an carcinoma. Nowadays, in order to optimize the ablative radio-iodine-therapy a stimulation of thyreoglobuline with rhTSH ( thyreotropin alfa) takes place instead of an hormone-deprivation. The dimension of the operative therapy depends on the kind of the illness and is most of the times accompanied by a medicamentous, hormonal and often radionuclide treatment. For example in case of a solitary toxic nodule, the removal of the knot, through a tiny cut in the skin, often is sufficient. Until a couple of years ago, a subtotal or almost total removal of the thyroid used to be recommended in case of a mutlinodular goiter and Graves’ disease. Nowadays a complete removal of the thyroid (thyroidectomy) is conducted in the most cases.
The neuromonitoring reduces the risk of an bilateral palsy of the vocal cord nerve (nervus laryngeus recurrens). In suitable cases a gland resection, in form of a minimal invasive (buttonhole) technique can be conducted. In this case a video assisted operation (VAT), take place through a two cm long, cosmetic cut in the skin fold. Usually in case of a carcinoma, a complete removal of the thyroid (total thyroidectomy) and where applicable a lymph nodule removal is indicated. In addition to the neurostimulation, microscopic technique are being used in order to conserve the vocal cord nerve and the parathyroid. The very best results are achieved by a surgeon with a large amount of experience in the field of thyroid-surgery.
Autor: Dr Andrzej Franczak