Seminar - Goitre

Abdul Waris Khan

Definition

• A goitre is an enlarged thyroid gland

Epidemiology

InternationalWorldwide, the most common cause of goiter is iodine deficiency.It is estimated that goiters affect as many as 200 million of the 800 million people who have a diet deficient in iodine.

Mortality/MorbidityMost goiters are benign, causing only cosmetic disfigurement. Morbidity or mortality may result from compression of surrounding structures, thyroid cancer, hyperthyroidism, or hypothyroidism.

SexThe female-to-male ratio is 4:1.

Pathophysiology

The thyroid gland is controlled by thyroid-stimulating hormone (TSH; also known as thyrotropin), secreted from the pituitary gland, which in turn is influenced by the thyrotropin-releasing hormone (TRH) from the hypothalamus. TSH permits growth, cellular

differentiation, and thyroid hormone production and secretion by the thyroid gland.

A deficiency in thyroid hormone synthesis or intake leads to increased TSH production. Increased TSH causes increased cellularity and hyperplasia of the thyroid gland in an attempt to normalize thyroid

hormone levels. If this process is sustained, a goiter is established. Causes of thyroid hormone deficiency include inborn errors of thyroid hormone synthesis,

iodine deficiency, and goitrogens.

Clinical features

• Goitres are present on examination in up to 9% of the• population.

• Most commonly a goitre is noticed as a cosmetic defect by the patient.

• The majority are painless, but pain or discomfort can occur in acute varieties.

• Large goitres can produce dysphagia and difficulty in breathing, implying oesophageal or tracheal compression.

• A small goitre may be more easily visible (on swallowing) than palpable.

• Clinical examination should record the size, shape, consistency and mobility of the gland as well as whether its lower margin can be demarcated (thus implying the absence of retrosternal extension).

• Examination should never omit an assessment of the patient’s clinical thyroid status.

• Specific enquiry should be made about any medication, especially iodine-containing preparations, and possible exposure to radiation.

Particular points of note are:■ Puberty and pregnancy may produce a diffuse increasein size of the thyroid.

■ Pain in a goitre may be caused by thyroiditis, bleedinginto a cyst or (rarely) a thyroid tumour.

■ Excessive doses of carbimazole or propylthiouracil willinduce goitre.

■ Iodine deficiency and dyshormonogenesis can also cause goitre.

Types

Diffuse Nodular

Diffuse goitre

• Simple goitre

• In this instance no clear cause is found for enlargement of the thyroid, which is usually smooth and soft. It may be associated with thyroid growth-stimulating antibodies.

• Autoimmune thyroid disease

• Hashimoto’s thyroiditis and thyrotoxicosis are both associated with firm diffuse goitre of variable size. A bruit is often present in thyrotoxicosis.

• Thyroiditis

• Acute tenderness in a diffuse swelling, sometimes with severe pain, is suggestive of an acute viral thyroiditis (de Quervain’s). It may produce transient clinical hyperthyroidism with an increase in serum T4

Nodular goitres

• Multinodular goitre

• Most common is the multinodular goitre, especially in older patients. The patient is usually euthyroid but may be hyperthyroid or borderline with suppressed TSH levels but normal T4 and T3. Multinodular goitre is the most common cause of tracheal and/or oesophageal compression and can cause laryngeal nerve palsy. It may also extend retrosternally.

• Solitary nodular goitre

• Such a goitre presents a difficult problem of diagnosis.

• Malignancy should be considered in any solitary nodule – however, the majority of such nodules are cystic or benign.

• A history of rapid enlargement, associated lymph nodes or occasionally pain in such a situation suggests the possibility of thyroid carcinoma.

• Risk factors for malignancy include previous irradiation, long-standing iodine deficiency and occasional familial cases.

• Solitary toxic nodules are quite uncommon and may be associated with T3 toxicosis.

• Fibrotic goitre

• Fibrotic goitre (Riedel’s thyroiditis) is a rare condition, usually producing a ‘woody’ gland. It is associated with other midline fibrosis and is often difficult to distinguish from carcinoma, being irregular and hard.

• Malignancy

• In addition to thyroid carcinomas, the thyroid is rarely the site of a metastatic deposit or the site of origin of a lymphoma.

Investigations

Thyroid function tests – TSH plus free T4 or T3

Thyroid antibodies – to exclude autoimmune aetiology.

Ultrasound. Ultrasound with high resolution is a sensitive method for delineating nodules and can demonstrate whether they are cystic or solid.

Chest and thoracic inlet X-rays to detect tracheal compression and large retrosternal extensions in patients with very large goitre or clinical symptoms.

Fine-needle aspiration (FNA). In patients with a solitary nodule or a dominant nodule in a multinodular goitre, there is a 5% chance of malignancy; in view of this, FNA should be performed.

Thyroid scan (125I or 131I) can be useful to distinguish between functioning (hot) or non-functioning (cold) nodules.

A hot nodule is only rarely malignant; however, a cold nodule is malignant in only 10% of cases and FNA has largely replaced isotope scans in the diagnosis of thyroid nodules.

Treatment

• Euthyroid goitre

• Many goitres are small, cause no symptoms and can be observed (including self-monitoring by the patient in the long term). In particular, during puberty and pregnancy a goitre associated with euthyroidism rarely requires intervention and the patient can be reassured that spontaneous resolution is likely.

Indications for surgical intervention are:

The possibility of malignancy. A history of rapid growth, pain, cervical lymphadenopathy, change in voice or previous irradiation to the neck are worrying features. A positive or suspicious FNA makes

surgery mandatory.

Pressure symptoms on the trachea or, more rarely, oesophagus. The possibility of retrosternal extension should be excluded.

Cosmetic reasons. A large goitre is often a considerable anxiety to the patient even though functionally and anatomically benign.

• Toxic nodule

• This is initially with antithyroid drugs but surgery or radioiodine is often required.

References

• Kumar and Clark clinical medicine 7th edition