hyperthyroidism
HYPERTHYROIDISM
Hyperthyroidism is the overactivity of the thyroid gland resulting in excessive production of thyroid hormones.
Symptoms are of gradual onset.
Earliest signs may be emotional lability and motor hyperactivity; decline in school performance may also be noted.
Causes are autoimmune (Grave's disease), inappropriate stimulation by trophic factors, passive release of preformed thyroid hormone stores in response to infections, trauma, or other offensive factors inside the body, and extra-thyroidal sources.

Diagnosis

Thyroid storm or thyroid crisis

  • An acute life-threatening exacerbation of hyperthyroidism
  • Signs & symptoms include high fever, changes in sensorium, restlessness, severe tachycardia & arrhythmia
  • May be precipitated by trauma, infection, dehydration

History

  • A comprehensive history should be elicited
  • Combination of ophthalmopathy & hyperthyroidism is suggestive of Graves’ disease
  • Most patients have (positive) family history of autoimmune thyroid disease

Physical Examination

  • Weight, height, & blood pressure (BP)
  • Heart rate (HR), cardiac rhythm, & respiratory rate (RR)
  • Inspect & auscultate the neck (check size, nodule, texture of goiter; thyroid bruit)
  • Ocular & lymphatic examination
    • Combination of ophthalmopathy & hyperthyroidism is suggestive of Graves’ disease
  • Dermatological examination (eg excessive sweating, onycholysis, vitiligo, alopecia)
  • Neurologic exam: Presence of tremors, proximal muscle weakness

Laboratory Tests

  • Obtain baseline CBC which includes WBC count with differential, and liver profile (ie serum alanine aminotrasferase, aspartate aminotransferase, gamma glutamyl transpeptidase, bilirubin)
Serum Thyroid-Stimulating Hormone (TSH) Levels
  • Recommended as initial diagnostic exam for patients suspected to have hyperthyroidism
  • Serum TSH measurement is highly sensitive & specific for the evaluation of hyperthyroidism
  • TSH levels are decreased in patients w/ hyperthyroidism
  • TSH receptor stimulating autoantibodies titers are elevated in Graves’ disease w/ 95% sensitivity & 96% specificity
    • Not routinely measured

Thyroxine (T4) Levels

  • Measure both total & free serum T4 levels
  • Free T4 improves diagnostic sensitivity/specificity when combined w/ measured TSH levels

Triiodothyronine (T3) Levels

  • Measure both total & free T3 levels; total T3 measurement preferred for diagnostic purposes
  • T3 levels may be more elevated than T4

Others

  • T4 binding globulin (TBG), transthyretin (TTR)

Imaging

Ultrasound

  • Useful in evaluating the size & shape of the thyroid, especially in large glands

Radioactive Iodine Uptake (RAIU) Test

  • Recommended to determine the cause of hyperthyroidism
  • Usually normal or elevated in the following: Graves disease, toxic adenoma, toxic multinodular goiter, trophoblastic disease, TSH-producing pituitary adenoma, T3 receptor mutation
  • Near-absent uptake with RAIU usually seen in the following: Silent thyroiditis, Amiodarone-induced thyroiditis, de Quervain’s thyroiditis, iatrogenic thyrotoxicosis, struma ovarii

Thyroid Scan

  • Recommended for patients with presence of thyroid nodularity

Disease Severity

Overt Hyperthyroidism

  • Increased T3, T4 levels, subnormal/undetectable TSH
  • Adrenergic manifestations are often more pronounced (eg tachycardia, anxiety, tremor) 


Subclinical Hyperthyroidism

  • Normal T3, T4 levels, low/undetectable serum TSH
  • Milder form of hyperthyroidism
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