Endocrine surgery

Published on 11/04/2015 by admin

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Last modified 11/04/2015

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11 Endocrine surgery

Most surgical endocrine disorders are neoplastic, autoimmune or genetic. These conditions may or may not result in endocrine dysfunction depending on whether there is abnormal hormone secretion. The principles of endocrine surgery have been crystallised by John Lynn and are summarised in Table 11.1.

Table 11.1 Principles of endocrine surgery

Principle	Example
Be convinced of the biochemical diagnosis	In Cushing’s syndrome, is the primary problem of pituitary or adrenal origin?
Make the patient safe	Control thyrotoxicosis in Graves’ disease, or hypertension in phaeochromocytoma
Localise the tumour(s)	In Conn’s syndrome, which side is the adenoma? CT and renal vein sampling may be necessary
Is an operation necessary?	Sometimes medical therapy is more effective, e.g. radioiodine for hyperthyroidism
Decide best technique	Open versus laparoscopic adrenalectomy

The thyroid

Embryology

The thyroid is derived from the foramen caecum at the junction of the anterior two-thirds and posterior third of the tongue. The gland migrates downwards in front of the foregut to lie anterior to the trachea but occasionally may descend lower to the superior mediastinum. It leaves behind the thyroglossal duct which may persist and form a thyroglossal cyst.

Surgical anatomy

The thyroid is fixed to the trachea by the pretracheal fascia so it moves up on swallowing. Aberrant thyroid tissues may be found anywhere along the embryological descent of the gland. Blood supply is from the superior and inferior thyroid arteries. Thyroid operations may damage important structures, highlighted in Table 11.2.

Table 11.2 Structures easily damaged during thyroidectomy

Structure	Result of injury
Recurrent laryngeal nerve	Paresis or paralysis of vocal cord: unilateral – hoarseness bilateral – stridor; change in voice; risk of aspiration
Parathyroid glands	Hypocalcaemia – severity depends on amount of tissue that remains
External laryngeal nerve	Paresis or paralysis of cricothyroid muscle – inability to achieve high-pitched notes

Thyroid function

The thyroid produces two types of hormones:

• T₃ and T₄, which regulate metabolic rate

• calcitonin, a calcium-regulating hormone which acts to decrease serum calcium by increasing bone uptake and renal excretion of calcium.

Thyroid pathology

The commonest thyroid disorders are:

• goitre (enlarged thyroid)

• hyperthyroidism (overproduction of T₃ and T₄ causing thyrotoxicosis)

• hypothyroidism (underproduction of T₃ and T₄ causing myxoedema)

• thyroid nodules

• thyroid cancers

• thyroiditis.

Goitre

A goitre is a diffuse enlargement of the whole thyroid gland. The patient may be hypothyroid, euthyroid or hyperthyroid, depending on the cause of the goitre. Causes include iodine deficiency, pregnancy, goitrogens, genetic abnormalities, Graves’ disease and Plummer’s syndrome.

Thyrotoxicosis

This is a common problem affecting 2% of females and 0.15% of males. The three main causes are:

• diffuse toxic goitre – Graves’ disease

• multinodular toxic goitre – Plummer’s syndrome

• toxic solitary nodule or adenoma.

Graves’ disease

This is the commonest cause of thyrotoxicosis, usually occurring between the ages of 20 and 40 years. Women are affected five times more often than males. Graves’ disease is due to an autoimmune process characterised by abnormal autoantibodies directed against thyroid TSH receptors. The natural history of Graves’ disease is one of intermittent remission and relapse. The thyroid is uniformly enlarged, firm and smooth, not nodular. Eye problems are common (Table 11.3). Thyroid function tests confirm an elevated T₃ and T₄ and reduced TSH. Anti-thyroglobulin and anti-microsomal antibodies are present when the cause is autoimmune.

Table 11.3 Eye abnormalities in Graves’ disease

Symptoms	Signs
Poor sight for both near and distant objects	Ophthalmoplegia
Double vision
Grittiness in the eye	Conjunctival oedema (chemosis)
Exophthalmos – protrusion of the globes	Exophthalmos
	Lid retraction
	Lid lag

Multinodular toxic goitre (Plummer’s syndrome)

A goitre that has been present for several years may subsequently become overactive. This is known as secondary toxic goitre (Plummer’s syndrome). Eye disease is unusual but cardiac arrhythmias and heart failure are common presenting features. The goitre is nodular and may displace the trachea, distinguishing it from Graves’ disease where the goitre is smooth and symmetrical. Thyroid autoantibody levels are normal.

Toxic solitary adenoma/nodule

This is a solitary autonomous adenoma occurring in 5% of cases of hyperthyroidism. A single nodule in the gland becomes overactive, causing suppression of all surrounding tissue, and may be diagnosed on an isotope scan because the nodule takes up the isotope but the surrounding gland does not. Eye disease is unusual.

Management of thyrotoxicosis

The underlying cause must be established since the definitive treatments depend on the underlying diagnosis. However, initial treatment is the same.

First, control the thyrotoxicosis with drugs. A combination of antithyroid drugs and beta-blockade is effective. Carbimazole is the initial antithyroid agent of choice. Agranulocytosis is a complication and the drug must not be used in pregnancy. Beta-blockade with propranolol reduces the effects of T₄ on the sympathetic nervous system and controls tachycardia and agitation.

Treat eye complications (seek ophthalmology opinion); see Table 11.4.

Table 11.4 Management of eye complications in Graves’ disease

Problem	Treatment
Exposed cornea with drying	Methylcellulose eye drops for lubrication
Failure of lid closure in marked exophthalmos	Tarsorrhaphy
Inflammation	Systemic steroids
Deterioration in sight from compressive optic atrophy	Surgical decompression of both orbits
Severe diplopia	Corrective surgery to eye muscles