Endocrinology Book

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Subclinical Hyperthyroidism

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  1. Definition
    1. Euthyroid patient with TSH suppression
  2. Epidemiology
    1. More common in the elderly
  3. Causes
    1. Multinodular Goiter
    2. Silent Thyroiditis (TSH normalizes within months)
    3. Pituitary abnormalities (Free T4 also suppressed)
    4. Early Hyperthyroidism in transition
    5. Partially treated Hyperthyroidism
    6. Iodine
      1. Recent radiocontrast administration (e.g. IVP)
      2. Other excessive iodine intake
    7. Medications
      1. Corticosteroids
      2. Dopamine
  4. Symptoms
    1. Significant Hyperthyroidism symptoms absent
    2. Nonspecific symptoms may be present
      1. Malaise
      2. Tachycardia
      3. Nervousness or anxiety
      4. Muscle Weakness
  5. Complications
    1. Overt Hyperthyroidism: 1-3% risk per year
    2. Atrial Fibrillation (relative risk: 3-5 in age > 60)
      1. Auer (2001) Am Heart J 142(5):838
    3. Increased Osteoporosis risk in postmenopausal women
    4. Increased Muscle Weakness and atrophy risk
  6. Labs
    1. Thyroid Stimulating Hormone (TSH) decreased
    2. Serum Free Thyroxine (Free T4) normal
    3. Serum Free Triiodothyronine (Free T3) nornal
  7. Imaging: 24 hour Radioactive Iodine Uptake Scan (RAIU)
    1. Increased >30% at 24 hours
      1. Grave's Disease
      2. Multinodular Goiter
      3. Autonomous Thyroid Nodule
    2. Decreased <5% at 24 hours
      1. Silent Thyroiditis
      2. Postpartum Thyroiditis
      3. Exogenous Thyroid hormone intake
  8. Evaluation
    1. Initial lab testing
      1. Thyroid Stimulating Hormone (TSH)
      2. Serum Free T4
      3. Serum Free T3
      4. Complete Blood Count (CBC)
      5. Chemistry panel
    2. Subsequent monthly testing for 3 months
      1. Thyroid Stimulating Hormone (TSH)
      2. Serum Free T4
      3. Serum Free T3
    3. Three month assessment
      1. Overt Hyperthyroidism (increased Free T4 or Free T3)
        1. Evaluate as Hyperthyroidism (including RAIU Scan)
        2. See Hyperthyroidism Management
      2. TSH below 0.1 with normal Free T4, Free T3
        1. Obtain 24 hour Radioactive Iodine Uptake Scan (RAIU)
        2. Consider Hyperthyroidism Management
      3. TSH between 0.1 to 0.45 with normal Free T4, Free T3
        1. Obtain 24 hour Radioactive Iodine Uptake Scan (RAIU)
          1. Evaluate for endogenous disease (e.g. Destructive Thyroiditis, Grave's Disease)
        2. Periodic re-evaluation of TSH every 3-12 months
  9. References
    1. Marqusee (1998) Endocrinol Metab Clin North Am 27:37
    2. Shrier (2002) Am Fam Physician 65(3):431
    3. Surks (2004) JAMA 291:228
    4. Woeber (1997) Arch Intern Med 157:1065

Decreased thyroid stimulating hormone level (C1295607)

ConceptsFinding (T033)
EnglishDecreased thyroid stimulating hormone level, Decreased thyroid stimulating hormone level -RETIRED-
Spanishdisminucion del nivel de tirotropina, disminucion del nivel de tirotropina - RETIRADO -
Parent ConceptsReason not stated concept (C1276325), Decreased level (laboratory finding) (C1290917)
SourcesSCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)



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