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Thyroid Stimulating HormoneAka: TSH, Serum TSH

Physiology
1. See Thyroid Physiology
2. Variation
  1. TSH levels follow a circadian rhythm
  2. EuThyroid individuals still have considerable variation in TSH levels over time
  3. 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
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
Increased TSH
1. Hypothyroidism
2. Drugs
  1. Haloperidol
  2. Chlorpromazine
  3. Metoclopramide
  4. Domperidone
3. TSH antibodies
4. Pituitary resistance
Decreased TSH
1. Hyperthyroidism
2. Acute illness
3. Hyponatremia
4. Malnutrition
5. Medications
  1. Dopamine
  2. Corticosteroids
  3. Bromocriptine
  4. Levodopa
  5. Pyridoxine

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This page was written by Scott Moses, MD, and was last revised 1/26/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 5.0.