Introduction

Patients with thyroid disorders presenting to a surgeon usually have a neck lump, often asymptomatic but the patient may fear malignancy. In some, the mass may be causing pressure symptoms or cosmetic deformity. A discrete thyroid lump may be found or the whole gland may be enlarged. A large thyroid swelling is known as a goitre, from the Latin for throat ‘guttur’. Most patients are clinically euthyroid (i.e. normal hormone activity) and thyroid function tests are normal. Occasionally patients are referred with hyperthyroidism when medical treatment has failed, radioisotope treatment is unsuitable or there is an overactive nodule. All may require some form of thyroidectomy.

Patients with parathyroid disorders usually attend because of symptomatic or biochemically detected hypercalcaemia caused by excess parathormone, treatable only by surgery for a solitary adenoma, multi-gland hyperplasia or, very rarely, carcinoma.

Diffuse or generalised enlargement of the thyroid

The term goitre is often used for any thyroid enlargement. Most large thyroid swellings in developed countries are simple colloid goitres i.e. idiopathic diffuse or multinodular hyperplasia. Multinodular goitres usually develop from diffuse goitres after some years.

Iodine deficiency is the usual cause of endemic goitres (often in isolated, mountainous regions such as Nepal), preventable by adding iodine to the diet. These are often asymmetrical, soft and composed of hyperplastic nodules, and can reach enormous sizes (see Fig. 49.1). Although unsightly, endemic goitres cause surprisingly few symptoms and the patient is usually euthyroid.

Anaplastic carcinomas may cause thyroid swellings in elderly patients (see Fig. 49.2), usually with symptoms of invasion including hoarseness (recurrent laryngeal nerve), and stridor, particularly at night, with tracheal invasion. The gland is hard on palpation. The uncommon thyroid lymphomas also present with diffuse enlargement.

In Graves’ disease (primary hyperthyroidism) there is usually some smooth thyroid enlargement, often increased by drug treatment but almost never the presenting feature. Similarly, in Hashimoto’s thyroiditis, the thyroid may be moderately enlarged but firm and finely nodular on palpation.

Solitary thyroid nodule

A clinically solitary thyroid nodule is common but 50% are multinodular on imaging (Fig. 49.3). When small, these nodules are found incidentally, often noticed when the patient swallows. Less than 10% of true solitary nodules are malignant although this rises to about 40% after neck irradiation. Almost all thyroid nodules in childhood are malignant. Fallout from the Chernobyl nuclear meltdown caused many thyroid cancers in children. Malignancy should be excluded in any solitary nodule, and FNA cytology or core needle biopsy is the first step.

A solitary nodule is usually idiopathic hyperplasia which if discrete, is a thyroid adenoma. Thyroid cysts are fairly common. Both fall within the description ‘simple or multinodular colloid goitre’.

Other features associated with thyroid enlargement

A new area of enlargement in an existing goitre may result from haemorrhage into a cyst or nodule, enlargement of a hyperplastic nodule or a developing carcinoma. If the gland extends into the anterior mediastinum behind the sternum (see Fig. 49.6, below), the trachea may be compressed or displaced by this retrosternal goitre and cause stridor, often only obvious when the neck is in certain positions, for example, sleeping on one side. Hoarseness or stridor may also result from invasion of trachea or recurrent laryngeal nerve by anaplastic carcinoma.

Pain and tenderness are uncommon presenting features, but characterise the rare infective de Quervain’s thyroiditis. Sometimes the thyroid is painful and tender in Hashimoto’s thyroiditis.

Hyperthyroidism

Clinical manifestations of hyperthyroidism are summarised in Box 49.1 (see also Fig. 49.4). Excessive thyroid hormone is a feature of Graves’ disease. Mild hyperthyroidism also occurs in the early stages of Hashimoto’s thyroiditis, burning out later with the patient becoming hypothyroid. A solitary adenomatous nodule may produce excess thyroid hormone causing hyperthyroidism. This is known as a toxic or hot nodule.

Hypothyroidism

Hypothyroidism is usually the late result of primary thyroid atrophy or Hashimoto’s thyroiditis, or treatment for hyperthyroidism. In any case, the gland is small and fibrous. Hypothyroidism is a late complication in up to 25% of patients after subtotal thyroidectomy and even more after radioiodine therapy for thyrotoxicosis, and is inevitable after total thyroidectomy. Hypothyroidism should be considered in surgical patients presenting with constipation and has also been implicated in aortic thrombosis in middle-aged women.

General thyroid status

First establish whether the patient is euthyroid, hyperthyroid or hypothyroid. Initially, this is clinical but estimations of free thyroxine (fT4) and TSH are usually performed. Thyroid-binding globulin is elevated in pregnancy and puberty; using free thyroxine level corrects for this and avoids misinterpretation. If the patient is clinically hyperthyroid but the fT4 is normal, tri-iodothyronine (T3) levels are occasionally measured. TSH level is usually low in hyperthyroidism and elevated in hypothyroidism. Some laboratories prefer to measure just the TSH level initially and perform detailed tests if this is abnormal.

Thyroid autoantibodies are assayed if autoimmune disease is a possibility. Although not usually measured clinically, the presence of long-acting thyroid stimulating factor (LATS) is diagnostic of Graves’ disease. Hashimoto’s thyroiditis is characterised by elevation of anti-thyroid antibodies such as anti-thyroglobulin or anti-mitochondrial antibodies (anti-thyroid M).

Morphology of the gland

Ultrasound scanning is useful to establish morphology and diagnose cysts. It can also indicate retrosternal extension. CT scans of neck and thoracic outlet are taken if malignancy is suspected or if there appears to be tracheal displacement or compression (Figs 49.6).

Tissue diagnosis

Tissue diagnosis using fine needle aspiration cytology (FNAC) or core needle biopsy is usual for solitary nodules or recently enlarged nodules in multinodular goitres. This can be performed without ultrasound, but ultrasound gives a fuller picture and guides biopsies. Given a competent and involved thyroid cytologist, 90% of thyroid nodules can be categorised this way. Needle core biopsy gives larger specimens with a greater diagnostic potential. If a colloid nodule is diagnosed, excision is not necessary unless it causes compressive symptoms or cosmetic deformity. Obviously malignant lesions require operation. These include papillary, medullary and early anaplastic carcinomas. Most lymphomas are inadequately sampled by FNAC or core biopsy and follicular carcinomas cannot be distinguished cytologically from benign follicular adenomas; both display sheets of follicular cells. Lesions with this appearance should be removed, although most will be benign.

Incision biopsy at open operation is occasionally used for diagnosing generalised thyroid enlargement where the chances of malignancy are low, or lymphoma is suspected.

Functional activity of glandular tissue

Injected radionuclides of iodine are avidly taken up by functioning thyroid tissue and used to be widely employed for thyroid scanning. The increasing use of ultrasound and needle cytology and knowing that only 10% of cold nodules are malignant have greatly reduced the need for radionuclide scanning.

When scanning is employed, the gland is imaged after isotope injection to identify the distribution of isotope activity. This may fall into one of four patterns:

Very occasionally, thyroid malignancies secrete thyroid hormones and show up as warm or hot nodules on isotope scanning. Isotope scanning can also identify and localise ectopic thyroid tissue (in the tongue or along the course of the thyroglossal duct), retrosternal extension of a thyroid swelling and metastases of functioning thyroid carcinomas, provided the thyroid has been removed or ablated.

Hyperthyroidism (thyrotoxicosis)

Two percent of women and 0.2% of men in the UK have hyperthyroidism. Untreated, it causes weight loss, anxiety, tachycardia, palpitations and increased risk of cardiovascular death. Most are caused by Graves’ disease, some by toxic multinodular goitre and a few by toxic adenoma. Carcinoma is a very rare cause, occasionally diagnosed incidentally when a hot nodule is examined histologically. Graves’ disease is an autoimmune disorder in which circulating antibodies bind to TSH receptors in the thyroid and stimulate follicular cells to secrete thyroid hormones independent of pituitary feedback. Hashimoto’s thyroiditis may produce mild hyperthyroidism in its early stages but is self-limiting. If in doubt, the aetiology can be determined by radioisotope scanning.