Goitre Flashcards
What is goiter
An enlarged thyroid gland due to any cause is called a goitre. For the gland to be palpable it must be at least 40g. Almost all diseases of the thyroid gland are associated with its enlargement. A goitre may be associated with:
I. Normal thyroid hormonal activity (euthyroidism)
2. Increased thyroid hormonal activity (hyperthyroidism). This is the commonest physiological disorder in our environment
3. Decreased or absent thyroid hormonal activity (hypothyroidism)
What are the classifications of goitre
Simple (non-toxic) Goitre (Endemic or Sporadic)
Toxic Goitre
Neoplastic Goitre
Inflammatory Goitre
What are some examples of inflammatory goitre
i) Auto-immunethyroiditis (Hashimoto’sdisease) and other types e.g. painless thyroiditis.
(ii) Acute suppurative thyroiditis
(iii) Subacute thyroiditis
(iv) Riedel’s tbyroiditis
(v) Specific infectivethyroiditis e.g. tuberculosis.
What are some examples of toxic goitre
(ii) Diffuse toxic goitre (Grave’s disease)
(ii) Toxic nodular goitre
(iii) Toxic nodule
(iv) (Rarelytoxic malignant tumour)
What is a simple goiter
A simple goitre is a goitre which is neither associated with increased nor decreased thyroid hormonal activity, and is also not neoplastic. It is therefore a goitre with normal thyroid hormonal functions.Simple goitre occurs in all communities of the world without regard for climate or race
What is the etiology of simple goitre
A simple goitre is ultimately caused by increased stimulation of the thyroid by oversecretion of TSH as a result of deficiency of the thyroid hormones (feed-back mechanism). Insufficiency of thyroid hormones may result from physiological states requiring increased metabolism or be pathological in origin
What is cause of inadequate thyroid hormones
Relative Physiological Deficiency: In physiological states such as puberty, menstruation, pregnancy or laccation, the body’s requirement of thyroid hormones is increased because of increased metabolic activity. If this is not met, TSH secretion is increased to stimulate the thyroid. The thyroid gland may therefore enlarge. Involution takes place when the hormones are increased in sufficient amount or the need for increased amounts is over. Repeated stimulation of the thyroid in females during menstruation and pregnancy accounts for their higher incidence of simple goitre.
2. Pathological Deficiency: Reduction of thyroid hormones may occur anywhere along their pathway of synthesis and release i.e. from iodine in the diet to release from thyroglobulin.
(i) The iodine in the diet and/or water may be inadequate. This is !he commonest cause of simple goitre. In endemic areas the soil is deficient in iodine. In limestone areas the water has a high calcium content which has goitrogenic effect.
(ii) Absorption of iodine from the gut may rarely be deficient.
(iii) Trapping and concentration of iodine by the thyroid may be prevented by drugs containing the ions perchlorate, penechnetate, thiocyanate and nitrate. Drugs such as para- aminosalicylic acid used in the treatment of tuberculosis, phenylbutazonefor rheumaroid arthritis, tolbutamide and chlorpropamide for diabetes mellicus are all goitrogenic.
(iv) Deficiency of enzymes necessary for oxidizing iodine, coupling of iodine and tyrosine, MIT and DIT or binding with and release from thyroglobulin leads to deficiency of thyroid hormones
(v) Excessive iodine paradoxically interferes with or- ganic binding of iodine and release ofhormones from the thyroid. Excess of iodine produces acute block of iodine binding (Wolff-Choikoff’s block) to tyrosyt residues in thyroglobulin. Excessive intake of iodine as in proprietary cough or asthma mixtures over a prolonged period may cberefore result in
“iodine” goitre.
Simple goitre is epidemiologically of 2 types:
l. Endemic goitre. 2. Sporadic goitre
What is an endemic goitre
Endemic goitre exists when more than 10% of any community have goitre. Areas of high incidence of endemic goitre in the world are in high rocky mountain regions. e.g. the Alpine Valleys, the Pyrenees, the slopes of the Himalayas and the Andes
Endemic goitre is mainly caused by insufficiency of iodine intake in the diet. The iodine contents of water-supply and the soil in granite mountain regions are very low. Other causesof endemic goitre are goitrogens in food and excessive calcium salts in water-supply. Cassava for instance contains cyanogeoic glucosideswhichyieldthiocyanate as a metabolic by-product. Thiocyanate inhibits iodine uptake by the thyroid.
What is sporadic goitre
When goitre occurs in an area where it is not endemic, it is said to be sporadic. Only a relatively small number of people are affected. It may be caused by genetic factors, pubertal growth, pregnancy, lactation, drugs and the causes of endemic goitre described above. The sporadic goitre is pathologically and clinically indistinguishable from endemic goitre
What is a diffuse hyperplastic (colloid) goitre
It is seen commonly in endemic areas, but also occurs sporadically. In endemic areas children may be affected, but girls from around puberty to 20 are those commonly involved. The gland is uniformly enlarged and soft and may occasionally be big enough to cause tracheal compression
What are the complications of nodular goitre
Pressure symptoms:
(i) On the trachea with difficulty in breathing. Sudden haemorrhage within a necrotic or cystic area may cause severe respiratory obstruction requiring urgent tracheostomy.
(ii) On the oesophagus with dysphagia,
(iii) At the thoracic inlet by a retrosternal goicre wich resulting distended jugular veins, oedema of the face and conjunctivae and respiratory difficulty.
(iv)Rarely on the recurrent laryngeal nerves with hoarse- ness of the voice.
2. Toxicity: Thyrotoxicosis may occur in a nodular goitre -secondary thyrotoxicosis.
3. Malignant Change: A nodular goitre may become malignant in 5-8% of patients, especially if there is associated iodine deficiency.
4. Infection: Rarely suppuration occurs with pain and tenderness in the gland, pyrexia and general malaise.
How do you investigate for goitre
I. Imaging: X-ray of the neck including the thoracic inlet in both anterio-posterior and lateral views and of the chest. A soft tissue swelling of the goitre will be shown. Diffuse or localized calcificationoccurs in many multi-nodular goltres,
The trachea is often displaced laterally and compression and narrowing usually associated with one lateral lobe goitre than in’alllobes’ goitre. maybe evident. A giant goitre often causes marked posterior displacement and retrolaryngeal extension, anteriordisplacement, and elongation and narrow·ing of the trachea. The trachea is often displaced laterally. Retrosternal extension of the goitre is also often diagnosed radiologically.
Ultrasound Scan: It is useful in distinguishing between solid and cystic swellings and can be used in children and pregnant women. It helps to determinethe actual size of ibe thyroid.
CT Scan: Stenosis oflhe trachea is best assessed with CT, especially in elderly patients with large recrosternal or recurrent goitre and associated respiratory problemswhich maybe due rather to a pulmonary or cardiac condition. MRI has a similar use to CT scan.
2 Thyroid function tests. It is essential to assay at least the serum Thyroid Stimulating Hormone (TSH) to exclude subclinical hypothyroidism or hypothyroidism, even if the serum T3 are not assayed or cost effectiveness.
3. Direct and indirect laryngoscopy to examine the vocal cords is essential in case there is asymptomatic paralysis of a recurrent laryngeal nerve
How do you prevent goitre
Iodine supplementation in food either in the form of iodized table salt or as iodized bread has been used to eradicate endemic goitre in many parts of the world
What is the drug therapy for goitre
Early cases of endemic goitre and sporadic goitre, especially the adolescent hyperplastic (colloid) goitres, can benefit from iodine therapy. Potassium iodide solutions like Lugol’s iodide or potassium iodide tablets may be safely prescribed. Thyroxine and its analogues are more effective in the management of diffuse hyperplastic simple goiter than iodine and are ‘widely used. They depress TSH secretion, the size of the thyroid is measured with an ultrasound. Neither iodine nor thyroxine is of much help in causing regression of established nodular goitre
What is the operative treatment for goitre
Thyroidectomy is the treatment of choice for simple nodular goitre for the following reasons:
l. The thyroid continues to grow and gets bigger and uffiightly.
2. lt may compress the trachea and cause respiratory obstruction. Bleeding may occur in it with sudden increase in size and tracheal obstruction.
3. It may become toxic.
4. It may compress the oesophagus.
5. It may compress the laryngeal nerve and cause hoarseness ofthe voice
6. Malignancy may occur
The type of thyroidectomy depends largely on what is found. Where all the lobes are involved, subcotal thyroidectomy is done. Where only one lobe is involved, lobectomy of the
infected lobe and removal of part of the apparently normal lobe sadvtsed, Even where a solitary nodule is found in one lobe,
subtotal thyroidectomy (including the nodule) is the best procedure. ‘Enucleation of a nodule’ should be avoided as it leads to recurrence in about 25 % of patients. In all cases the pyramidal lobe should be specially looked for and removed whether enlarged or not. If this is not done, the patient may return with a mid-line neck swelling (goitre pyramidal is). The isthmus should also be removed to prevent a recurrent goitre developing from the isthmus.
A big, diffuse hyperplastic (colloid) goitre causing pressure symptoms also requires subtotal thyroidectomy.
However, total thyroidectomy through capsular dissection, which essentialJy is bilateral lobectomy and isthmusectomy, is another option because of the possibility of incidental carcinoma and the development of recurrent goitre which may be more difficult co treat.The patient is placed on thyroxine for life. The complicationof total thyroidectomy are not significantly different from chose of partial thyroidectomy in large volume centres and when the technique of capsular dissection is used. In developing countries, compliance to life-long therapy ispoor.
Minimally invasive, video-assisted thyroidectomy can be done for a nodule < 3 cm in diameter and thyroid lobe volume of < 50ml on ultrasound
