Management of thyroid disorders

Interpretation of biochemical tests

High thyroid-stimulating hormone (TSH)

  • with high free T4
    • Assay interference
    • ? TSH secreting pituitary tumour
    • ? Thyroid hormone resistance
  • with normal free T4
    • Subclinical hypothyroidism (TSH greater than 4.5 mU/L less than 20 mU/L)
  • with low free T4
    • primary hypothyroidism or thyroiditis (TSH usually greater than 20 mU/L)

Normal TSH

  • with high free T4
    • Assay interference
    • ? TSH secreting pituitary tumour
    • ? Thyroid hormone resistance
  • with normal free T4
    • normal
  • with low free T4
    • Sick euthyroid
    • secondary hypothyroidism

Low TSH

  • with high free T4
    • Thyrotoxicosis
    • Thyroiditis
  • with normal free T4
    • Free T3 raised: thyrotoxicosis, thyroiditis
    • Free T3 normal: subclinical hyperthyroidism
  • with low free T4
    • secondary hypothyroidism

 

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