Evidence-Based Exam: Thyroid

Anatomy

Source: Siminoski K. JAMA. 2008

The thyroid gland is located in the anterior neck and usually consists of 2 lobes connected at their lower midregions by a transverse isthmus.

  • A few landmarks can help us locate the isthmus, noting that there is wide variability among patients in the position of the following structures. The most prominent structure in the anterior neck is the thyroid cartilage (the V at the top is the laryngeal prominence of the thyroid cartilage). Inferior to the thyroid cartilage lies the cricoid cartilage (usually 3 cm below the laryngeal prominence), and inferior to this lies the isthmus of the thyroid gland. The isthmus is normally around 1.5 cm wide and usually 4 cm below the laryngeal prominence.

Each thyroid lobe lies against the sides of the trachea, extending up from the isthmus to the region of the cricoid and thyroid cartilages and downward toward the clavicles. Each lobe is normally 4-5 cm long. The posterior portion of each lobe lies beneath the belly of the ipsilateral sternocleidomastoid (SCM) muscle. Because the fascial envelope of the thyroid gland is continuous with the pretracheal fascia of the cricoid cartilage and hyoid bone, the thyroid ascends and descends with the laryngeal structures during swallowing.

  • If the laryngeal prominence and suprasternal notch of the manubrium are far apart (separated by >10 cm), the patient may have a conspicuous “high-lying” thyroid, which resembles a goiter despite being of normal size.
  • If the laryngeal prominence is close to the suprasternal notch (separated by <5 cm), the patient has a “low-lying” thyroid, which often is concealed behind the SCM muscles and clavicles, making complete palpation of the gland impossible. Low-lying thyroids are more common in elderly patients.

Exam

Inspection

Two maneuvers make the thyroid more conspicuous: extending the neck (which lifts the trachea and thyroid, and stretches the skin against the thyroid) and inspecting the patient’s neck from the side (which may help reveal subtle bulging or asymmetry).

  • Observing the patient swallow may enhance shadowing or bulging of an underlying mass, and may improve visualization of a low-lying thyroid gland.

Palpation

The patient’s neck (i.e., slightly flexed) should be relaxed to allow for palpation. Much has been said about an anterior versus a posterior approach in palpating the thyroid gland, but neither approach has been shown to be superior.

General approach:

  1. Ask patient to extend neck
  2. Place three fingers along midline of the neck below chin
  3. Locate the thyroid cartilage (often called the Adam’s apple)
  4. Move fingers inferiorly until you reach cricoid cartilage
  5. Palpate the isthmus of the thyroid
  6. Palpate each thyroid lobe by moving fingers laterally to both sides
  7. Have patient swallow to assess symmetry of elevation
    • During a normal swallow, both the thyroid and trachea make an initial upward movement of 1.5-3.5 cm; the larger the oral bolus, the greater the movement
  8. The clinician should note the thyroid’s size, consistency (e.g., soft, firm), texture (e.g., diffuse, nodular), tenderness, tracheal deviation, and lymphadenopathy

A number of other approaches exist for palpation, each with certain advantages:

  • Lahey’s method appears best for palpating the lateral and posterior lobes as well as tumors, nodules, thickness, and remnants after thyroidectomy
  • Crile’s method appears best for small solitary thyroid nodules
  • Pizzillo’s method appears best for patients with obesity or a short neck

Potential exam findings

  • Goiter: Often subtle, a good rule of thumb is a lateral lobe is likely enlarged if it is larger than the distal phalanx of the patient’s thumb. Large goiters may extend from the neck to the superior mediastinum, passing through the inflexible thoracic inlet (i.e., the bony ring formed by the upper sternum, first ribs, and first thoracic vertebral body). At the thoracic inlet, such goiters may compress the trachea, esophagus, or neck veins and thus produce dyspnea, dysphagia, facial plethora, cough, and hoarseness. Sometimes, when these patients flex or elevate the arms, the thoracic inlet is pulled up into the cervical goiter, just as if the thyroid were a cork and the thoracic inlet were the neck of a bottle
    • Pemberton’s sign: If a patient with retrosternal goiter elevates the arms, dramatic facial congestion may occur (i.e., positive sign). This finding occurs because the thoracic inlet (“neck of the bottle”) is an inflexible bony ring formed by the first thoracic vertebra, first ribs, and upper sternum. A normal-sized thyroid is too small to obstruct the thoracic inlet. In contrast, a goiter of sufficient size may obstruct the thoracic inlet, especially if the goiter extends below the sternum and the patient elevates the arms (which pulls the thoracic inlet, or “neck of the bottle,” up into the goiter, or “cork”).
  • Thyroglossal duct cyst: May present at any age, appearing as tense, nontender, mobile, nonlobulated round tumors, usually at the level of the hyoid bone (which is above the thyroid cartilage) along the midline. Asking the patient to protrude their tongue causes a thyroglossal duct cyst to move upward and protrude.
  • Thyroid nodule: Rarely palpable (and much more often found incidentally on ultrasound)

Other potential exam findings

  • Lymphadenopathy: The neck has a complex lymphatic network, necessitating systematic palpation.
  • Bruits: A thrill may be palpated with the fingers placed gently over the thyroid gland.
  • Hypothyroidism: xerosis (dry skin), preorbital puffiness, delayed relaxation phase of reflexes, dry coarse hair or alopecia, bradycardia, non-pitting edema
  • Hyperthyroidism: diaphoresis and moist palms, thickened skin (especially pre-tibial), bulging eyes (lid retraction or proptosis), eye irritation, periorbital edema, diplopia, change in visual acuity, hyperreflexia, tachycardia

Further reading!

  • JAMA’s The Rational Clinical Examination: Does this patient have a goiter? by Kerry Siminoski
  • Evidence-Based Physical Diagnosis, by Steven McGee

Blog post based on Med-Peds Forum talk by Madeleine Ward, PGY4

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