CHAPTER XXVII

THE THYREOID GLAND

Surgical Anatomy--Physiological hyperaemia--Acute thyreoiditis--GOITRE--Varieties: _Parenchymatous_; _Adenomatous_; _Cystic_; _Malignant_; _Toxic_.

#Surgical Anatomy.#--The _thyreoid gland_ consists of two lateral lobes connected by an isthmus. The lateral lobes lie in contact with the side of the larynx up to the middle of the thyreoid cartilage, and with the sides of the first five or six rings of the trachea. The isthmus lies in front of the second, third and fourth rings of the trachea, and from it a process of gland tissue--the _pyramidal lobe_--passes up in the middle line towards the hyoid bone.

The gland lies under cover of the superficial muscles of the neck, and is surrounded by a process of the cervical fascia--the external thyreoid capsule of Kocher--which connects it with the larynx, trachea, and oesophagus, so that it moves with these structures on swallowing. In this capsule are numerous veins; and in the groove between the oesophagus and trachea the recurrent (laryngeal) nerve runs. Enclosing the gland substance is the capsule proper, which sends in processes to form its fibrous stroma. The arteries of supply--the superior and inferior thyreoids--are very large for the size of the gland, and enter it at its four corners. The thyreoidea ima, when present, goes to the isthmus. Isolated nodules of thyreoid tissue--_accessory thyreoids_--are sometimes met with in different parts of the neck; they are liable to the same diseases as the main gland.

The secretion of the gland is absorbed into the general circulation through the veins; it consists of a complex colloid substance which contains an iodine-albumin--iodothyrin--and plays an important part in maintaining the normal metabolism of the body, particularly of the central nervous and cutaneous tissues in adults, and of the bones in children. Disturbance of the function of the thyreoid gland plays a part in producing the symptoms characteristic of myxoedema, cretinism, and goitre.

The _para-thyreoid glands_--usually two on each side--lie in the external capsule along the posterior edge of the lobes of the thyreoid. They are flattened, elliptical bodies, averaging a quarter of an inch in length and an eighth of an inch in width, of a light brown colour, smooth and glistening on the surface, and of a soft, flabby consistence (W. G. MacCallum). When tetany follows operations for goitre it is due to the removal of these glands.

#Physiological Hyperaemia.#--The thyreoid varies greatly in size even within normal limits, and may become engorged and swollen from physiological causes, particularly in the female. Before the onset of menstruation at puberty, for example, the thyreoid frequently becomes engorged, and the enlargement may recur with each period for months or even years. During pregnancy also the gland may become swollen.

#Acute Thyreoiditis# may occur in a healthy thyreoid or in one that is the seat of goitre, and may end within a few days in resolution, or go on to suppuration. It is due to infection with pyogenic bacteria, which usually gain access to the gland by the blood stream, as, for example, in typhoid fever, pyaemia, influenza, and other acute infective diseases. Direct infection sometimes occurs from an abscess, a cellulitis, or an infected wound in the neck; it has also occurred from a foreign body impacted in the oesophagus ulcerating through and perforating the gland.

One lobe is usually more involved than the other, but the condition may be diffused. When pus forms it may infiltrate the stroma of the gland, or may be collected into several small foci.

_Clinical Features._--The usual signs of inflammation are present; there is severe headache of a congestive nature, and sometimes vertigo. The swelling takes the shape of the thyreoid, and although the skin may not be red, the subcutaneous veins are dilated. In severe cases there is pain and difficulty in swallowing and dyspnoea.

When suppuration ensues, all the symptoms are aggravated, and repeated rigors occur. The pus may burst into the cellular tissue of the neck, or into the air-passage or the oesophagus.

_Treatment._--In the non-suppurative stage the ordinary treatment of acute inflammatory conditions is employed; if pus forms, the abscess should be opened and drained.

#Tuberculous and syphilitic affections# of the thyreoid are very rare.

PARENCHYMATOUS GOITRE OR BRONCHOCELE

The term goitre is applied clinically to any non-inflammatory enlargement of the thyreoid gland.

_Etiology._--Parenchymatous goitre, sometimes called also simple, or non-toxic goitre, is endemic in certain hilly districts in England--particularly Derbyshire and Gloucestershire--and in various parts of Scotland. It is exceedingly common in certain valleys in Switzerland. It is met with less frequently in men than in women, and it occurs chiefly during the child-bearing period of life. The toxic agent that causes goitre has been traced to certain mountain springs in goitrous districts; it has been observed that a patient with goitre may, through faecal contamination apparently, infect the water supply, and that conscripts in order to avoid military service have drunk from goitrous springs with success. Children born in a goitrous district are liable to be cretins, while if goitrous parents move to a healthy district, the children are born healthy. If the water supply of a goitrous valley be changed to a healthy spring, goitre and cretinism disappear. Thorough boiling of the water rids it of its toxic properties.

_Morbid Anatomy._--Both the secreting and the fibrous elements share in the hyperplasia, and the gland as a whole becomes enlarged and forms a horseshoe-shaped swelling of moderate size in the neck. This swelling is soft and smooth on the surface, and is seldom quite symmetrical. In some cases the hypertrophy involves chiefly the isthmus. In others an outlying accessory lobule of thyreoid tissue constitutes the bulk of the swelling, and this may extend a considerable distance from the position of the normal thyreoid, reaching even behind the sternum into the thorax--_infra-thoracic_ or _retro-sternal goitre_.

When the secreting elements increase out of proportion to the stroma, numerous rounded or irregular spaces filled with a thick yellow colloid material are formed in the substance of the goitre--_colloid goitre_. The majority of these spaces are not larger than a pea, but one or more may enlarge and form cysts of considerable size--_cystic goitre_. These varieties, especially the cystic form, attain greater dimensions than any other form of goitre.

When the fibrous stroma is greatly in excess--_fibrous goitre_--the swelling is smaller, firmer, and shows a greater tendency to contract and compress the trachea. If the sclerosis is extreme and the secretory tissue undergoes atrophy, myxoedema may result.

In some cases the hyperplasia affects chiefly the blood vessels of the thyreoid--_vascular goitre_. The capillaries, veins, and arteries are increased in size and number; the swelling pulsates and increases in size when the patient makes any muscular effort. Haemorrhagic cysts may also develop in the substance of these goitres.

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_Effects on the Trachea._--The trachea may be _displaced laterally_ when the enlargement of the gland affects one lobe more than the other; or it may be _compressed and narrowed_ from side to side--the _scabbard trachea_--when both lobes are about equally affected and the enlargement extends posteriorly so as almost to surround the air-passage (Figs. 278, 279). The third effect is that of _softening of the cartilaginous rings_ of the trachea so that the air-tube, instead of having a considerable degree of elastic resiliency, is soft and flaccid and readily yields to pressure. Under these conditions an alteration in the attitude of the patient, from the erect or sitting to the recumbent position, would appear to be sufficient to permit of a compression of the trachea.

Further changes in the trachea consist in catarrh and engorgement of the blood vessels of its mucous membrane, attended with an abundant secretion of mucus, which, if it accumulates behind a narrowed segment of the trachea, may still further encroach on the lumen.

_Pressure on other Structures._--The _recurrent nerve_ may be pressed upon intermittently causing spasms and choking, or continuously causing abductor paralysis and hoarseness.

The gullet is rarely compressed; if marked difficulty in swallowing develops, some additional factor should be suspected, notably carcinoma at the junction of the pharynx with the oesophagus. The carotid arteries are displaced laterally beneath the sterno-mastoids without detriment; the superficial veins--anterior and external jugular--are greatly distended in those cases in which the goitre grows downwards behind the sternum.

_Clinical Features._--The symptoms vary widely in different cases, and their severity is not proportionate to the size of the goitre. The disfigurement produced by the swelling is often the only cause of complaint. In some cases the symptoms are due to the pressure of the enlarged thyreoid on surrounding structures. In others toxic effects, in the form of cardiac, nervous, muscular, and general metabolic disturbances, predominate, and are due to absorption of excessive or abnormal thyreoid secretion. This thyreoid toxaemia varies in degree; in the milder cases it merely amounts to a nervousness or excitability that may unfit the patient for occupation; it reaches its maximum in the condition of hyperthyreoidism characteristic of exophthalmic goitre or Graves' disease (p. 614).

The skin over the goitre is freely movable, and the tumour itself can be moved transversely, carrying the larynx and trachea with it, but it cannot be moved vertically. It moves up and down with the larynx on swallowing--a point of great diagnostic value. Of the mechanical symptoms dyspnoea is the most constant. It may only amount to shortness of breath on exertion, or the patient may suffer from sudden and severe dyspnoeic attacks, especially when lying on the back during sleep, and such an attack may prove fatal. This may be due to the weight of the tumour pressing on the trachea, which has been softened and distorted by the goitre, or to temporary congestion and engorgement of the mucous membrane of the air-passages. In these cases there is marked stridor both on inspiration and expiration, but no aphonia. In rare cases the goitre presses upon the recurrent nerve, causing spasmodic dyspnoea, hoarseness, and aphonia from impaired movement of the vocal cords, and these symptoms, especially if accompanied by pain, raise the suspicion of malignancy. Disturbance of the heart's action may cause palpitation and sudden attacks of syncope; and pressure on the blood vessels may give rise to a feeling of fullness in the head, and giddiness.

The occurrence of haemorrhage into the substance of the goitre or into a cyst, produces a sudden aggravation of the symptoms.

In _intra-thoracic_ or _retro-sternal goitre_ the tumour displaces and compresses the trachea and causes dyspnoea, and there are occasional paroxysmal attacks of breathlessness, which may be mistaken for asthma, particularly as the patient is usually the subject also of bronchitis and emphysema. In some cases the patient can, by a violent expiratory effort, such as coughing, project the goitre upwards into the neck. When the goitre is fixed in the thorax, the clinical features are those of a mediastinal tumour with lateral displacement of the trachea, and engorgement of the veins of the neck.

_Treatment._--The patient should change his residence to a non-goitrous district. The evidence regarding the benefit derived from the internal administration of thyreoid extract, or of preparations of phosphorus or of iodine, is conflicting.

Operative treatment is indicated when there are symptoms referable to pressure on the air-passage, and in goitres which are steadily increasing in size. Kocher considers it advisable to operate if the patient becomes breathless on making pressure on the goitre from side to side. The suspicion of a goitre becoming malignant is also a reason for removing it by operation.

The operation--_thyreoidectomy_--consists in excising that portion of the thyreoid which is causing pressure symptoms, and this usually involves removal of one-half of the gland. The chief danger in operations for goitre is cardiac insufficiency, as evidenced by disturbed rhythm of the heart-beats, lowering of the blood pressure, or dilatation of the cavities of the heart (Kocher).

It is sometimes advisable to perform the operation under local anaesthesia. A general anaesthetic is, however, preferred in this country. The injection of 1/6th grain of morphin and 1/120th grain of atropin half an hour before the operation, and the administration of ether by the open method, or by intra-tracheal insufflation, is safe and satisfactory.

There is reason to believe that the absorption of thyreoid secretion squeezed from the divided surfaces gives rise to a condition known as _acute thyreodism_ during the first few hours after operation; its symptoms are elevation of temperature, increase in the pulse-rate (150-200), rapid respiration with dyspnoea, flushing of the face, muscular twitchings, and mental excitement. The gentle handling of the tumour and the employment of a drainage tube for the first forty-eight hours diminishes this risk.

_Tetany_, as evidenced by the occurrence of cramp-like contractions of the thumb and fingers, may supervene within a few days of the operation if one or more of the para-thyreoids have been inadvertently removed. It may be controlled by large doses of calcium lactate. On no account may the whole of the thyreoid gland be removed, as this is followed by the development of symptoms closely resembling those of myxoedema--_operative myxoedema_ or _cachexia strumipriva_.

_Treatment of Sudden Dyspnoea._--When dyspnoea suddenly supervenes and threatens life, it is sometimes possible to relieve the pressure on the trachea by open division of the skin, superficial fascia, platysma and deep fascia in the middle line of the neck, so as to relax the tension on the goitre. If this is insufficient, the isthmus may be divided. Should relief not follow, tracheotomy must be performed, and a long tube or a large-sized gum-elastic catheter with a terminal aperture be passed along the trachea beyond the seat of obstruction.

#Adenoma of the Thyreoid.#--In this condition the swelling of the thyreoid is due to the growth within its substance of one or more adenomas of variable size and surrounded by a capsule. The rest of the gland may be normal, or may show some degree of hyperplasia. Some are solid, others undergo cystic degeneration, the glandular tissue being replaced by a quantity of clear or yellowish fluid, sometimes mixed with blood. The cysts thus formed may be unilocular or multilocular, and intra-cystic papillary vegetations frequently grow from their walls. The walls of the cysts may be thin, soft, and flaccid, or thick and firm, or they may even be calcified.

The thyreoid is enlarged, but instead of the uniform enlargement which characterises the parenchymatous goitre, it tends to be uneven, with hillocky projections corresponding to the individual cysts (Fig. 280), and in these fluctuation may be detected. It is to be noted that there are no toxic symptoms in cystic adenoma.

The treatment is necessarily operative; cystic tumours may be tapped and injected with iodine, but the more satisfactory procedure, both with the solid and cystic forms, is to incise freely the overlying thyreoid tissue and enucleate the tumour.

#Malignant Disease of the Thyreoid.#--This, whether in the form of _carcinoma_ or _sarcoma_, usually develops in a gland that has been the seat of goitre for several years, although it may begin in a previously healthy gland.

_Clinical Features._--Both sexes, above the age of fifty, are affected in about equal proportion. The characteristic features are that the tumour undergoes a progressive increase in size, that it becomes fixed to its surroundings, that its surface tends to be uneven and nodular, and its consistence densely hard. The voice often becomes hoarse from abductor paralysis due to infiltration by the growth, usually of the left recurrent nerve. The effects upon the trachea are more decided and more progressive than in parenchymatous goitre; it displaces and compresses the trachea and frequently overlaps it, so as to bury the air-passage completely. If the tumour tissue has actually penetrated the trachea, the expectoration is tinged with blood. Dysphagia is rarely a prominent symptom. The lymph glands become enlarged after the tumour bursts through the capsule; and metastases to the lungs and bones, particularly the skull, sternum, and mandible, are common. When the goitre extends behind the sternum--the _malignant form of retro-sternal goitre_--the pressure symptoms are due to the encroachment upon the limited accommodation of the upper opening of the thorax; the trachea especially suffers, and the pressure on the veins causes distension of the anterior and external jugulars and their tributaries. The patient is unable to lie down; there are violent paroxysms of coughing, and an abundant frothy expectoration. Death may take place suddenly from asphyxia, from heart failure, or from displacement of a thrombus from one of the veins in the neck.

_Treatment._--It is only in the earliest stages that a malignant goitre can be successfully removed. In the later stages complete extirpation is not to be attempted, as it usually involves the removal of a portion of the trachea or oesophagus, and the operation is attended with grave risk to life.

Operative interference is often called for, however, for the relief of respiratory embarrassment. _Tracheotomy_ may prove a difficult and dangerous procedure, owing to the trachea being buried under the goitre and displaced or narrowed by it, so that it is not easy to reach it or to introduce an efficient tube beyond the point of obstruction. A more certain method consists in exposing the goitre by an incision as for thyreoidectomy, rapidly removing sufficient of the growth to expose the trachea and admit of a tube being introduced. If there is a retro-sternal prolongation compressing the trachea within the thorax, a long flexible tube may have to be passed beyond the site of the compression before the dyspnoea is relieved. The benefit is immediate and decided; the accumulated secretion is coughed up, and after a few deep breaths the patient is able to lie down, and usually falls asleep. The stridor disappears. Unfortunately the relief is only temporary, and the patient soon succumbs to a broncho-pneumonia, or to secondary haemorrhage from the trachea.

#Toxic Goitre#--#Exophthalmic Goitre#--#Graves'# or #Basedow's Disease#.--These terms are applied to a variety of goitre in which the symptoms due to absorption of thyreoid secretion--_thyreotoxicosis_--predominate. The name "exophthalmic goitre" is misleading, as in some cases the enlargement of the thyreoid, and in others the eye symptoms, are scarcely appreciable, while the general symptoms are well marked. The term toxic goitre or _hyperthyreoidism_, suggested by C. H. Mayo, is preferable, as the manifestations of the disease depend upon excessive or abnormal action of the thyreoid tissue.

The condition is chiefly met with in young adult women, and may develop suddenly after a shock to the nervous system. The intoxication affects the higher cerebral functions and causes nervousness, irritability, and tremor; the cardiac and vaso-motor centres, causing tachycardia and pallor of the skin; the sympathetic fibres to the eye, causing protrusion of the eyeballs, staring of the eyes without winking, narrowing of the palpebral fissure, dilatation of the pupil, and lagging behind of the upper lid, and sometimes also of the lower lid--von Graefe's symptom. There may be diarrhoea and vomiting, loss of weight, and in the worst cases there is delirium at night. In course of time there develops cardiac insufficiency with fibroid degeneration of the myocardium. Coagulation of the blood is retarded, and there is a marked diminution in the number of leucocytes, especially the neutrophils, and an increase in the lymphocytes (Kocher).

In the early stages the thyreoid is enlarged and pulsatile, and bruits may be heard over it; later, these vascular symptoms disappear, and only a firm, diffuse, uniform swelling implicating all parts of the gland remains.

_Prognosis._--The tenure of life is uncertain as the patient offers little resistance to intercurrent affections such as influenza and pneumonia. If the average course of the disease is represented by a curve, the greatest height is reached during the second half of the first year and then descends. For the next two to four years it fluctuates with occasional exacerbations of symptoms due to fright or worry.

_Treatment._--Medical measures, along with the external application of radium, the strict observance of rest in bed with the exclusion of all forms of excitement and worry, the administration of bromides, heroin or other sedatives, and of digitalis or other cardiac tonics, are to be prescribed in the first instance, and in any case, as a desirable preparation for operation.

_Operative measures_ consist in the _ligation_ of the vessels and nerves at one or other pole of the gland--usually the superior on one side--followed by, if necessary, a partial _thyreoidectomy_.

Crile of Cleveland has organised his clinic in the direction of arranging that the operation shall be performed without the patient knowing that it is to take place--what he calls "stealing the goitre"--the thorough preparation of the patient for the operation, the minimising the risk from the anaesthetic by the combination of novocain locally and of nitrous oxide and oxygen; and of diminishing the risk of absorption of thyreoid secretion by packing the (open) wound with gauze wrung out of a solution of flavin.

Operations on the cervical sympathetic cord have been abandoned.

The presence of toxic goitre may influence the question of operation in the treatment of other surgical conditions, and may determine the selection of one or other form of anaesthesia.