Thyroid and Its Disorders

Anatomy of thyroid

  • Landmarks: laryngeal prominence (adam’s apple) of thyroid cartilage and cricoid cartilage which lies below it
  • Isthmus of thyroid normally lies just below the cricoid cartilage
  • High vs low lying thyroid
    – If distance between laryngeal prominence and the suprasternal notch is far (eg 10cm), the thyroid gland maybe high lying (pseudogoiter)
    – If laryngeal prominence is close to suprasternal notch (<5cm), the thyroid gland is low lying (and located retrosternally). Palpation maybe impossible.

Inspection of thyroid gland

  • See from the side. The line between cricoid prominence and suprasternal notch (where the thyroid gland is located) is a straight line.
  • If it is bowed, consider goiter

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Palpation

  • An easier way to palpate thyroid gland

What do we palpate?

  • Size
  • Consistency (hard or soft)
  • Nodular
  • Tenderness

The key to know that what we palpate is thyroid gland is

  • It moves during swallowing, and then hesitate a while before returning. As thyroid gland and tracheal is connected by ligaments.
  • If it does not move during sallowing or does not hesitate before returning to its original position, it is likely not thyroid gland.

Cervical goiter

Estimation of size

  • Rule of thumb: lateral lobe is enlarged if it is larger than distal phalanx of the patient’s thumb
  • WHO grading

Retrosternal goiter

  • May cause TOS, SVC syndrome and compression of trachea and esophagus
  • TOS (thoracic outlet syndrome):
    – Compression of brachial plexus: pain in the multiple myotomes in UE
    – Compression of subclavian vein: UE venous thrombosis (Paget-Schroetter syndrome)
  • SVC syndrome:  elevated JVP + plethora + facial & arm edema
  • Compression of trachea and esophagus: dyspnea, stridor, dysphagia

Thyroglossal cyst

  • Cystic swellings of thyroglossal duct , an epithelium lined remnant marking the descent of thyroid tissue from the base of tongue to its final location
  • Midline neck mass
  • Characteristic sign is upward movement when the patient protrudes the tongue

Delphian node

  • Prelaryngeal lymph node
  • Named Delphian because it is the first one exposed during surgery and its appearance often foretells what the surgeon will find in thyroid.
  • Radiologically, it is situated in lymph node level VI
  • If it’s palpable, it is usually enlarged – suspect malignancy or Hashimoto’s thyroidits

Hypothyroidism

  • Classical triad of puffy skin + delayed reflexes + thick & nasal speech
  • Features
    – Skin: dry, cold, puffy skin
    – Achlles reflex: delayed reflex due to prolonged contraction & relaxation
    – Hypothyroid speech: slow, deep and nasal (as if patient has a cold)
  • Billewicz Diagnostic Index for hypothyroidism
    >30 has a high likelihood of hypothyroidism

Graves disease

  • Triad of prominent eyes + goiter + tachycardia
  • Auscultation in thyroid gland can often ellicit bruit (in 70% of patents)
  • Eye findings:
    Lid lag: von Graefe sign
    – ask patient to look down, the upper eyelid “lags” behind

    Lid retraction: Dalrymple’s sign
    – ask patient to look straight, white sclera is seen between the limbus and the lid margin; usually the lid margin rests just below the corneal limbus

    Graves opthalmopathy
    –  NO SPECS
    – Consider if patient with Graves disease complain of gritty sensation in the eyes or diplopia

  • CV findings:
    – Loud S1
    – Tachycardia
    – Means Lerman scratch (systolic rub resembling scratching near the left 2nd ICS)
  • Skin findings:
    – Moist (due to increased sweating) and warm
    – Pretibial myxoedema
  • Neuromuscular findings
    – Fatigue & weakness
    – Fine tremor due to sympathetic overflow
    – Brisk ankle reflexes

** Other ddx of lid retraction

  • Facial palsy: unilateral weakness of orbicularis oculi –> levator palpebrae is no longer being opposed
  • Unilateral ptosis: attempts to elevate the weakened lid causes excessive neural signals which end up elevating another lid
  • Previous eyelid surgeru

More eponyms?

Von Graefe: lid lag (We look down in Grief !)

Darylrmple sign: lid retraction (DaryLRmple)

Joffroy sign: lack of forehead wrinkling (FF resembling wrinkling)

Stellwag sign: staring look (Stellwag for Staring)

Moebius sign: Poor convergence (Merging Of EyeBalls Is UnSuccessful)

Wayne Diagnostic Index for hyperthyroidism >20 points have a high likelihood for hyperthyroidism


Note: BOTH hypo and hyperthyroidism cause amenorrhea !

  • Hypothyroidism: increased TRH causes increased prolactin production which blocks GnRH
  • Hyperthyroidis: multiple mechanisms, but likely linked to high SHBG which leads to high ratio of bound estradiol. Only free estradiol can induce a LH peak.

Mnemonic for THYROID disorders: NEVER FORGET THEM AGAIN !

THYROIDISM

  • Tremor (in hyper)
  • Heart Rate
  • Yawn (fatigue in both)
  • Reflexes (brisk or delayed)
  • Oligomenorrhea
  • Intolerance to temperature  (heat or cold)
  • Diarrhea (or constipation)
  • Increased or decreased appetitie
  • Skin (cool,dry and puffy or moist and warm skin)
  • Myxoedema (facial puffiness in hypothyroidism, pretibial myxoedema)

Reference:

Steven McGee. Evidence Based Physical Diagnosis. Pg 250-276

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