Lab

Thyroid Stimulating Hormone

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Thyroid Stimulating Hormone, TSH, Serum TSH, Thyrotropin

  • Physiology
  1. See Thyroid Physiology
  2. Variation
    1. TSH levels follow a circadian rhythm
      1. TSH will vary as much as 1-2 uIU/ml over the course of the day
      2. Consider drawing TSH at the same time of day for longterm serial measurements
    2. TSH levels increase with normal aging in euthyroid patients
      1. Consider using age-adjusted TSH interpretation
      2. Age 20-29: 3.56 mIU/ml is 97th percentile
      3. Age >80: 7.49 mIU/ml is 97th percentile
      4. Surks (2007) JCEM 92: 4575 [PubMed]
    3. Pregnancy
      1. See Thyroid Dysfunction in Pregnancy
      2. See Hypothyroidism in Pregnancy
      3. Maintaining euthyroid state in pregnancy is critical
    4. Euthyroid individuals still have considerable variation in TSH levels over time
    5. Populations of euthyroid individuals also have considerable variation in TSH levels
  3. Regulation
    1. Negative feedback
      1. Unbound Thyroxine (Free T4)
      2. Unbound Triiodothyronine (Free T3)
    2. Positive Stimulation
      1. Thyroid Releasing Hormone (TRH)
  • Interpretation
  • Non-Pregnant
  1. Normal
    1. Random: 0.3 - 5.0 uIU/ml
    2. Following Thyroid Releasing Hormone (TRH) stimulation
      1. TSH: 9-30 uIU/ml at 20-30 min
  2. Borderline Increased: 5-10 uIU/ml
  3. High: >10 uIU/ml
  • Interpretation
  • Pregnancy
  1. Non-pregnanct: 0.3 to 4.3 mIU/ml
  2. First trimester: 0.1 to 2.5 mIU/ml
  3. Second trimester: 0.2 to 3.0 mIU/ml
  4. Third timester: 0.3 to 3.0 mIU/ml
  5. Abbassi (2010) Obstet Gynecol 114(6): 1326-31 [PubMed]
  • Causes
  • Increased TSH
  1. Hypothyroidism
  2. Drugs
    1. Amiodarone
    2. Lithium
    3. Haloperidol
    4. Chlorpromazine
    5. Metoclopramide
    6. Metyrapone
    7. Domperidone
  3. TSH antibodies
  4. Pituitary resistance
  • Causes
  • Decreased TSH
  1. Hyperthyroidism
  2. Euthyroid Sick Syndrome (associated with acute illness)
  3. Pituitary disease causing TSH deficiency
  4. Hyponatremia
  5. Malnutrition
  6. Mood Disorders
  7. Medications
    1. Amiodarone
    2. Interferon
    3. Interleukin-2
    4. Opiates
    5. Corticosteroids
    6. Levodopa
    7. Dopamine Agonists
    8. Pyridoxine
    9. Bromocriptine
    10. Somatostatin analogs
    11. Carbemazepine
    12. Metformin