The Thyroid

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, as better skills may guide a more intelligent use of costly scans and better assessment of the likelihood of hyperthyroidism in anxious young patients.

A

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 ( 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 backward 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. As 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.

  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.

• 7.

  What is Marañón’s sign ?

  Vasomotor erythema over the neck after stroking the skin over the throat in patients with Graves’ disease. It was first described by the Spanish endocrinologist, Gregorio Marañón (1887–1960).

B

Thyroid Gland Palpation

• 8.

  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.

• 9.

  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”).

• 10.

  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.

• 11.

  What is the average size of the thyroid 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 that are just 1.5 times normal size (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 size) are usually large enough to be appreciated even by novices.

• 12.

  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 ).

    

• 13.

  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 the 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 101).

C

Additional Components of the Focused Thyroid Examination

• 14.

  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.

• 15.

  What additional aspects of the neck exam are important in thyroid evaluation?

  • Scars indicative of previous thyroid surgery

  • Redness at the base of the neck (Marañón’s sign)

  • Venous engorgement (especially after Pemberton’s maneuver)

  • Tracheal shift

  • Lymphadenopathy (especially Delphian node[s] – see Chapter 18 , Lymph Nodes, Question 30)

  • Transillumination of nodules and cysts

• 16.

  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 size (i.e., 40 gm), multinodular goiters are usually the most prominent offenders. When a large mediastinal or substernal thyroid obstructs the superior vena cava (SVC), 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.

  

• 17.

  What is the Pemberton’s maneuver ?

  A reversible 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 ).

  

• 18.

  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:

  • Goiter and positional head and neck symptoms

  • A large cervical goiter

  • Evidence of substernal extension of the gland

  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.

• 19.

  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.

• 20.

  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.

• 21.

  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’.

• 22.

  How do you distinguish a thyroid bruit from other neck sounds?

  By location:

  • 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.

• 23.

  What is Berry’s sign ?

  An absent carotid pulse in patients whose cancer has invaded the vascular bundle. Always a sign of malignant thyromegaly.

• 24.

  Who was Berry?

  Sir James Berry (1860–1946) was a Canadian surgeon who contributed extensively to the field of thyroid resection. During World War I, he also was a philanthropist, assembling with his first wife a medical team and then traveling to Serbia. Captured by the Hungarians, he was forced to repatriate, but eventually returned to Eastern Europe to continue his humanitarian work.

• 25.

  How can one categorize thyroid abnormalities?

  By assessing both physical findings and endocrine function ( Table 8.1 ).

  Table 8.1

  Physical Findings and Disease Processes

  THYROID FINDING	FUNCTION	DISEASE PROCESS
  Diffuse Enlargement
  Diffuse, smooth goiter	Normal	Simple goiter, endemic goiter
  Multiple nodules	Normal/hyper/hypo	Multinodular goiter
  Diffuse, bosselated goiter	Hyper	Graves’ disease
  Firm, small, nontender goiter	Hypo	Chronic thyroiditis (Hashimoto’s)
  Firm, diffuse tenderness	Hyper/hypo	Subacute thyroiditis
  Firm, hard, fixed, unmovable gland	Normal	Malignancy
  Firm, hard, with lymphadenopathy	Normal	Malignancy
  Focal tenderness	Normal/hypo	Abscess
  Focal Enlargement
  Toxic with thyroid nodule	Hyper	Functional adenoma (Plummer’s)
  Transilluminated nodule	Normal	Thyroid cyst
  Nontoxic with thyroid nodule	Normal	Malignancy
  Focal tenderness, hyperthyroid	Normal	Hemorrhage in functional adenoma

D

Goiter

• 26.

  What is the normal thyroid size?

  “Normal” depends on iodine supply in the local diet. In the not-too-distant past, for example, thyroids became progressively larger as one ascended from the sea to the mountains. In fact, euthyroid goiters were so common in the Swiss and Italian Alps that they became part of the local folklore. For example, one of the most colorful of the Commedia dell’Arte masks was Gioppino, an Alpine mountaineer whose trademark sign was a gigantic goiter ( Fig. 8.10 ). The very word cretin (in reference to endemic and congenital hypothyroidism) also has something to do with mountaineers and goiters. Sapira reminds us that some early Christians ran to the Pyrenees to escape persecution. They escaped successfully, but also acquired hypothyroidism, and the mental slowing associated with it. When traveling to different villages, they were easily recognized and immediately referred to as cretins ( Chretien is French for Christian). Huge goiters still occur, but only in mountainous regions (like the Himalayas), where iodinated salt is not routinely instituted.

  

• 27.

  Why is estimating size clinically important?

  Because in patients with suspected or known disease, size can:

  • confirm thyroid involvement

  • help with differential diagnosis

  • guide and interpret laboratory testing

  • guide selection of therapy

  • help monitoring

  For example, in patients presenting with symptoms of hyperthyroidism, an enlarged gland increases the likelihood of thyrotoxicosis, whereas a normal-sized gland makes anxiety more likely. Moreover, Graves’ disease patients presenting with a larger goiter are less likely to undergo immunologic remission during antithyroid therapy, thus favoring radioactive iodine (whose dose is also based on the size of the gland). Finally, evaluation of size can help monitor response to treatment. For example, shrinking of a large goiter after hormonal replacement suggests effective suppression.

• 28.

  What is a goiter?

  From the Latin guttur (throat), this is a chronic enlargement of the gland ( Fig. 8.11 ). Goiters occur endemically in iodine-deficient areas and sporadically elsewhere. As Sapira reminds us, the Latin for goiter is struma , a term still occasionally used, even though originally it did not indicate an enlarged thyroid, but instead a scrofula (i.e., the widening of the neck that makes the patient resemble a sow [ scrofula in Latin]). Although this was mostly due to tuberculous lymphadenopathy, it eventually became linked to the thyroid after the Struma river of Bulgaria, an area of endemic goiter.

  

• 29.

  What is the threshold for a goiter?

  Some authors have suggested the “rule of thumb,” which defines as enlarged a lobe the size of the thumb’s distal phalanx. Alternatively, one could calculate the volume of each lobe by multiplying width by depth by length, and then multiplying the result by 2.

• 30.

  Are goiters neoplastic?

  No. Cancers are usually nodular , even though at times they may be goitrous.

• 31.

  So what is the nature of goiters? Are they euthyroid?

  Goiters are neither neoplastic nor inflammatory, but rather hypertrophic or degenerative . They do not reflect functional status either, since enlargements may occur in both euthyroid and dysthyroid states (either hypo- or hyper-). Overall, most goiters are eu thyroid (80%); 10% are hypo thyroid, and 10% hyper thyroid. Hence, they usually present as asymptomatic masses.

• 32.

  What are the three most common forms of a goiter?

  Multinodular goiter, Hashimoto’s thyroiditis, and Graves’ disease. In euthyroid subjects, think of multinodular goiter and Hashimoto’s; in hypothyroid patients, think of Hashimoto’s; and in hyperthyroid patients, think of Graves’ and multinodular goiters (Graves’ also will have unique skin and eye manifestations).

• 33.

  What about subacute thyroiditis?

  It usually presents with tenderness , which can often mimic pharyngitis. Thyromegaly is otherwise modest (1.5–3 times normal). Note that the differential diagnosis of a painful and tender gland also should include spontaneous hemorrhage into a cyst or nodule.

• 34.

  Is goiter common in pregnancy?

  No. Usually, there is a silent and postpartum thyroiditis that may manifest itself as a goiter, although only half of the patients present as such (most are instead hyper thyroid). Otherwise, a true goiter is rather uncommon in pregnancy. Yet, mild hypertrophy is frequent, especially because of the changed hormonal milieu. In the past, this was even used as a “poor man’s” (or woman’s) pregnancy test. For example, overbearing Roman fathers used to keep a keen eye on their daughter’s neck by periodically measuring its circumference, so as to detect, as early as feasible, any possible “loss of purity.”

• 35.

  What is the prevalence of goiter in iodine-replete countries?

  Very low. If we define as “normal” a thyroid <10 gm (with an upper limit of 20), the prevalence of goiter in iodine-replete countries is about 2% in men and 10% in women.

• 36.

  Can goiters be easily differentiated from normal glands?

  Yes. Normal thyroids are barely visible and only slightly palpable due to interference by various surrounding structures, especially the SCMs. Hence, the first sign of a goiter is usually an increase in size of the lateral lobes, which become easily palpable. This is followed by a visible enlargement of the entire gland , first on lateral neck inspection and then on frontal view (with the neck extended). By the time the goiter is large enough to become palpable, it can be spotted from both front and sides.

• 37.

  What may lead to false-positive and false-negative results of goiter detection?

  • (a)

    False-positive thyroid enlargement (pseudogoiter)

    • Accentuated prominence of a palpable but in reality normal gland:

      • Thin patients whose thyroid is uniquely and misleadingly accessible.

      • Patients with long and curving neckline that makes the thyroid quite prominent in spite of its normal location and size. Such pseudogoiters have been dubbed the Modigliani syndrome, after the Italian artist’s penchant for long and lordotic necks. They are the most common cause of referral for possible goiter.

      • Patients whose thyroid is higher than usual in the neck. These account for 10% of all referrals. Important clues are a negative thumb sign and a laryngeal prominence that is more than 10 cm above the suprasternal notch.

    • The presence of a fat pad in the anterolateral neck (common in young women and obese patients). In contrast to the thyroid, the fat pad does not rise with swallowing.

    • Anterior neck masses . These can be easily differentiated from goiters by using swallowing. Branchial cleft cysts, cervical lymphadenopathy, and pharyngeal diverticula are all less likely to adhere to laryngeal structures, and thus will not rise with deglutition. Goiters instead will. One important exception is the thyroglossal duct cyst, which not only rises with swallowing but also does so upon forced tongue protrusion (see Chapter 7 , The Neck, Questions 10–15).

  • (b)

    False-negative thyroid enlargement

    • Inadequate examination skills . The most common reason for a false-negative exam.

    • Short and thick-necked patients , especially if obese, elderly, or with chronic obstructive pulmonary disease (COPD).

    • Atypical or ectopic placement of the thyroid . Instead of being cervical , the goiter may be substernal or retroclavicular. Laterally placed lobes, obscured by the SCMs, also may yield false-negative results.