Chapter 8 The Thyroid
A. Generalities
The thyroid may not be the most important organ in a busy general practice, but in physical diagnosis it is second only to the heart in number of examination errors and lack of physician’s confidence. This is unfortunate, since better skills may guide a more intelligent use of costly scans and better assessment of the likelihood of hyperthyroidism in anxious young patients.
B. Anatomic Review And Thyroid Gland Inspection
1 What are the thyroid’s landmarks?
They are the laryngeal prominence and cricoid cartilage. Start your exam by identifying the hyoid bone, a horseshoe mobile structure just under the mandible, so called because of its “upsilon” like shape. Immediately below it, you will find the thyroid cartilage, which can be readily identified by its V shape, the midline notch on the superior edge (laryngeal prominence), and its being the most prominent structure in the anterior neck (Adam’s apple). Just below it, separated by a little gap (the cricothyroid recess), is the horizontal ring of the cricoid cartilage. The thyroid isthmus lies immediately below, 4 cm from the laryngeal prominence. It connects the two lateral lobes of the gland by crossing the trachea over the second, third, and sometimes even the fourth ring. Note that while the distance between isthmus and landmarks (cricoid cartilage and laryngeal prominence) is constant in all individuals, the distance between laryngeal prominence and suprasternal notch is variable. This may result in glands that are either low lying or high lying in the neck (see Fig. 8-1).
2 Where are the thyroid lobes in relation to other neck structures?
The lateral lobes fan out from the midline isthmus just below the cricoid cartilage, curve posteriorly around the sides of trachea and esophagus, and then ascend backwards and upward like the two branches of a V (Fig. 8-2). Each lobe is 3–5 cm long, so that the lower margin reaches down to 2 cm above the clavicle (and fifth to sixth tracheal ring), whereas the upper margin extends instead upward to the middle of the thyroid cartilage. Except for its isthmus, the thyroid is covered by thin, strap-like muscles, of which only the sternocleidomastoid muscles (SCMs) are visible. Since the fascial envelope of the gland is continuous with the pretracheal fascia of both the hyoid and cricoid, the isthmus will ascend and descend with the larynx upon swallowing. This is important because it helps in distinguishing the thyroid from other neck structures.
3 What is the pyramidal lobe?
An upward extension of one of the lobes, usually the left, present in up to 50% of autopsies. Rarely palpable in the normal-sized gland, it is detectable in 10–15% of nontoxic goiters.
4 What is the best way to Inspect the thyroid?
By having the patient either stand or sit, with the head slightly tipped backward (around 10 degrees), and the cervical muscles as relaxed as possible. Neck extension is beneficial for two reasons:
It raises the trachea further up from the suprasternal notch, thus moving upward any low-lying thyroid, too.
It tightens the skin over the gland, thus enhancing visualization. Slight contralateral flexing of the neck also may accentuate a mass, nodule, or gland asymmetry.
Once the patient is well positioned, inspect the midline, 2–3 cm above the clavicles. Look within the SCMs for the inferior margins of the thyroid lobes, and then locate the isthmus (just below the cricoid cartilage). Finally, inspect the superior margins of the lobes (which should barely touch the sides of the thyroid cartilage). Look also for any possible pyramidal lobe. Use cross-illumination with a penlight to better accentuate shadows and nodules. Observing the gland from the side also may help detect possible protrusions. Note that unless a goiter is present, there should be no bulging between cricoid cartilage and suprasternal notch. Hence, a goiter is effectively ruled out if the gland is not visible on lateral view of an extended neck. Once inspection is complete, assess the associated venous structures of the neck, and record any possible abnormality (Figs. 8-3 and 8-4).
5 How helpful is swallowing during inspection or palpation?
Quite helpful. According to some authors, it may raise the sensitivity of inspection to that of inspection and palpation combined. Although its role has not been formally studied, most skilled examiners do ask patients to swallow during inspection (and even palpation) for the following reasons:
Swallowing modifies the shadows of thyroid irregularities or masses, thus enhancing their visual detection.
It raises the gland, thus making it more accessible to both inspection and palpation.
It slides the gland (or its irregularities) against the examiner’s hands, thus improving tactile discrimination and recognition.
Most importantly, it allows the examiner to localize the abnormality because only the thyroid, lower trachea, and larynx move with swallowing. Deglutition lifts up both the trachea and thyroid by 1.5–3.5 cm. This movement culminates in a brief moment of hesitation, followed by a return of both the larynx and thyroid to their original location. Any mass that does not follow this triple sequence is not in the thyroid.
6 Should the patient be given a glass of water?
Probably yes, since the extent to which laryngeal and thyroid structures move upward is proportional to the amount of swallowed bolus. Give patients a glass of water and ask them to hold a sip in their mouth until given the command to swallow. Repeat as needed.
7 How much information can be gained by inspection?
Quite a bit, thanks to the gland’s superficial position in the anterior neck. Inspection can tell us about location, size, shape, symmetry, and surface. It also can teach us about mobility with swallowing, thus distinguishing the thyroid from other neck structures.
C. Thyroid Gland Palpation
9 What are the goals of palpation?
To confirm size, location, shape, symmetry, and mobility of the gland—all previously identified through inspection. Palpation also can assess texture and consistency as well as fluctuance or tenderness—focal or diffuse. A hard thyroid, for example, suggests cancer, whereas a rubbery one is typical of Hashimoto’s disease. Palpation also can identify a solitary nodule or the multiple bumps of a multinodular goiter. It can detect the diffuse, fine, and rounded protuberances of Graves’ disease, whose gland is as bosselated as a raspberry. In these patients, a diffusely enlarged and soft goiter (i.e., one with the consistency of surrounding tissues) suggests a hypervascular Graves’ thyroid, whereas a firm goiter argues instead for an infiltrated gland, as in the later phases of the disease. Finally, tenderness in a firm and diffusely nodular gland argues for subacute thyroiditis, whereas tracheal deviation and cervical adenopathy suggest cancer.
10 What does the normal gland feel like?
Like the meat of an almond. In fact, each lobe is the size of a whole almond, no larger than the distal phalanx of the thumb (“rule of thumb”).
11 Should a normal thyroid be palpable?
Not necessarily. Glands of 15–20 gm (upper limit of normal) are barely palpable, whereas smaller ones (10–15 gm) are almost never detectable. Since thyroid size in a population is largely determined by dietary iodine supply, glands tend to be larger in deficient areas. Iodine supplementation has lately reduced the upper limit of normal from 35 to 20 gm in the United States, even though it remains 35 in iodine-deficient regions. This means that even a palpable thyroid may be “normal” in some parts of the world.
12 What is the average size of the gland?
Lobes are 2 cm wide, 4–5 cm high, and 2.5 cm deep. The isthmus is 1.25–2 cm wide (and high) and <0.6 cm deep. Weight is 10–20 gm, and volume <20 mL. Still, it is more convenient (for both physician and patients) to categorize thyroids as normal and palpable or normal and nonpalpable. Experienced examiners can easily palpate small goiters of up to 1.5 times normal (25–30 gm). In fact, in some iodine-deficient regions, glands of this sort may be considered nongoitrous. Thyroids weighing 40 gm (i.e., twice normal) are usually large enough to be appreciated even by a first-year student.
13 How do you palpate a thyroid?
Unlike inspection, palpation comes in many forms, including bimanual or single hand and anterior or posterior. None has been shown to be better.
Start with proper positioning. In contrast to inspection, a slight ipsilateral flexion and rotation of the neck may allow you easier access to a mass, nodule, or gland asymmetry. Hence, to palpate the right lobe, ask the patient to flex and rotate the neck toward the right. Do the opposite for the left lobe. Yet, as for inspection, a slight neck extension (10 degrees) may help, too, by lifting the top of a substernal goiter into a more accessible position. Still, most experts recommend flexion over extension. Finally, ask the patient to swallow repeatedly while you palpate the moving gland.
The posterior bimanual approach is the most commonly used. While standing behind the patient, place the index and middle fingers of both hands along the midline of the neck, just below the chin. These should be 2 cm above the suprasternal notch, and 0.5 cm inside the medial margin of the SCM. From that position, locate first the thyroid cartilage, then slide gently down to the horizontal groove that separates it from the cricoid cartilage. This is covered by the cricothyroid membrane, which overlies the first tracheal ring and represents the reference point for emergency tracheostomy (cricothyroidotomy) in upper airway obstruction. Continue sliding down until you reach the next well-defined tracheal ring. At this point, you are on the thyroid isthmus, which lies between the cricoid cartilage and suprasternal notch, and is almost never palpable. Slide your fingers laterally on the isthmus, and go around for approximately 2–3 cm along each side: you will be touching the two main lobes of the gland. Use a soft touch to minimize discomfort and maximize yield. If the gland is enlarged, evaluate its consistency. Then ask yourself whether the enlargement is asymmetric or bilateral, nodular or diffuse, with movable overlying layers associated with adenopathy. Use one hand to fix the trachea and the other to palpate one lobe at a time (Figs. 8-5 and 8-6). You can practice by placing the second and third fingers of both hands over your own sternal notch. Move them up 2 cm above the clavicles (toward the lower thyroid poles), then palpate each lobe in detail.
The anterior single-hand approach. Face the patient and use the thumb plus the index finger of one hand to palpate each lobe. Do this just inside the SCMs (Fig. 8-7).
14 What are the normal variants in size and location?
Women have larger and more easily palpable glands.
In 1% of the population, the entire left lobe (or its lower half) is absent.
The right lobe is often larger than the left.
A pyramidal lobe presents as a triangular projection, arising from the isthmus and extending up toward the hyoid. It feels like thyroid, and it moves with deglutition.
Posterior, extracapsular, and ectopic tissue can occur in 5% of normal glands. This usually extends from the posterior aspect of the tongue toward the pyramidal lobe, and occasionally down into the mediastinum (see Chapter 6, Nose and Mouth, question 103).
D. Additional Components Of The Focused Thyroid Examination
15 What other aspects of the general exam should be emphasized?
If you suspect an autoimmune disorder (such as Graves’), search for extrathyroidal signs—especially in the eyes and integument (nails and skin). Search also for findings of dysthyroidism.
17 What are the potential complications of a large goiter?
Mostly obstructive, with impaired venous return (facial plethora) and a compression of the esophagus and trachea that may result in dysphagia and dyspnea. Stridor occurs in 10% of substernal goiters; tracheal deviation in one third. Although Graves’ glands may be up to two times normal (i.e., 40 gm), multinodular goiters are usually the most prominent offenders. When a large mediastinal or substernal thyroid obstructs the superior vena cava, there will be venous engorgement over the anterior chest and neck and possible impairment of cerebral venous return (Fig. 8-8). If reversible, all these findings can be unmasked by the Pemberton’s maneuver.
18 What is the Pemberton’s maneuver?
A reversible superior vena cava (SVC) obstruction caused by a substernal goiter being “lifted” into the thoracic inlet as a result of arm raising. This makes the goiter behave like a “thyroid cork,” blocking the inlet and thus preventing venous return. To carry out the maneuver, ask the patient to elevate the arms above the level of the head, as if surrendering (“elevat[ing] both arms until they touch the sides of the head,” in Pemberton’s words). If the sign is present, “after a minute or so, congestion of the face, some cyanosis, and lastly distress become apparent.” In fact, the test is considered positive when the patient experiences either facial plethora (blue or pink suffusion of the neck and/or face due to venous stasis) or head congestion, dizziness, and stuffiness. If severe, the “thyroid cork” may even cause dyspnea and hypotension. The test is negative if nothing happens after 3 minutes of arm elevation (Fig. 8-9).
Figure 8-9 Pemberton’s sign. A 58-year-old woman with a 20-year history of goiter presented with a 2-month history of progressive dyspnea on exertion, occasional stridor, and a choking sensation while supine. She had previously been asymptomatic. A, Physical examination revealed a diffusely enlarged thyroid with no palpable nodules and undetectable lower poles. B, Within 30 seconds after raising both arms simultaneously (Pemberton’s maneuver), marked facial plethora (Pemberton’s sign) developed, indicating compression of the jugular veins. Serum thyrotropin and free thyroxine concentrations were normal. C, Computed tomography of the neck revealed a large goiter extending into the anterior superior mediastinum and causing compression and deviation of the trachea. The patient underwent thyroidectomy, and her symptoms resolved. Pathologic examination revealed a multinodular goiter.
(From Basaria R. Pemberton’s sign. N Engl J Med 350:1338, March 25, 2004, with permission.)
19 What is the significance of a positive Pemberton’s maneuver?
Facial plethora after arm raising (Pemberton’s sign) is diagnostic of increased pressure in the thoracic inlet. It is also prognostic, since these patients often have more severe disease, with airway compromise, reduced peak expiratory flow, and thrombosis of right subclavian and axillary veins. Hence, the maneuver should be used in all patients with:
Note that venous obstruction is not uncommon in substernal goiters, which present with distended neck and thoracic veins in 10–20% of the cases. Although rare, full-blown SVC syndrome also may occur. Still, many patients usually have few physical signs—with the possible exception of the inability to palpate the lower pole of the gland. This should serve as a clue to the presence of a substernal goiter. When in doubt, have the patient swallow, extend the neck, or carry out maneuvers that increase intrathoracic pressure—such as coughing or Valsalva’s or Pemberton’s.
20 Is Pemberton’s sign specific for a substernal goiter?
No, it may be encountered in other patients with reversible SVC syndrome because of lymphomas or upper mediastinal tumors. It also may occur in thoracic outlet obstruction.
21 Who was Pemberton?
Hugh Spear Pemberton (1890–1956) was a graduate of Liverpool University, and to Liverpool he returned after serving in WWI, practicing at Northern Hospital till his sudden death in January 1956 (just a year after retirement). An endocrinologist with an interest in diabetes, he also published on thyrotoxicosis, peripheral vascular disease, and hospital planning. The description of his homonymous sign appeared in a brief letter to The Lancet in 1946. Within 3 years the maneuver was on Bailey’s 1949 Demonstration of Physical Signs in Clinical Surgery, and then in most physical examination textbooks.
22 When should one auscultate the thyroid?
Whenever a goiter presents with signs of hyperthyroidism. A bruit reflects the gland’s increased vascularity—rare in simple thyrotoxicosis, but common in Graves’.
23 How do you distinguish a thyroid bruit from other neck sounds?
A venous hum is heard lower in the neck than a thyroid bruit. It is also suppressed by compression of the ipsilateral neck veins. Note that the continuous character of a “hum” cannot reliably differentiate it from a bruit, since 20–36% of all hyperthyroid patients have indeed a continuous bruit (due to arteriovenous communications within the hyperplastic gland). Compression of neck veins will help differentiate the two.
A carotid bruit is heard higher and lateral to the gland than a thyroid bruit.
A thyroid bruit can be differentiated from the transmitted murmur of aortic stenosis or aortic sclerosis through a complete cardiac exam, very much like the stridor and hoarseness that often accompany thyromegaly.
24 What is Berry’s sign?
An absent carotid pulse in patients whose cancer has invaded the vascular bundle. Always a sign of malignant thyromegaly.
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