Clinical Criteria
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History taking to evaluate patients at risk
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Symptoms/signs of thyroid hormone deficiency
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Evidence of disease/ previous treatment or exposure known to cause thyroid/pituitary/ hypothalamic failure
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Conditions associated with increased risk of chronic autoimmune thyroiditis
Laboratory Testing
Specific tests
 | Include measurement of TSH, T4 or FT4 (FreeT4),T3 or, FT3 (FreeT3) |
In primary hypothyroidism
Decreased T3, T4 levels with elevated TSH or
Normal T3 lowT4 and high TSH /
LowT3 occurs in severe cases
In sub clinical hypothyroidism
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| Normal T 3, T4 levels with elevated TSH levels |
In central hypothyroidism
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| Low T 3, and T 4 levels with normal or low TSH |
Interpretation of T 3, T 4, TSH levels
T3,T4 Normal
TSH Normal
T3, T4 Normal
TSH High
T3, T4 Low
TSH High or
T3, T4 Low
TSH Normal or
T3 Normal
T4 Low
TSH High
T3, T4 Low
TSH Low
Normal
Subclinical
Hypothyroidism
Primary
Hypothyroidism
Central
Hypothyroidism
|
| In autoimmune thyroid disease causing hypo- thyroidism, antimicrosomal antibodies are present in 90% of patients. |
Neonatal screening for congenital hypothyroidism
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| It was introduced in 1974.. |
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| This has improved the prognosis of patients with congenital hypothyroidism. |
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| Ideally, screening should be done with T 4 and TSH levels by 4th day of neonatal life and reconfirmed by with following values. |
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| FT4 < 6ug/dl and TSH > 20-40 uIU /L |
In case of central hypothyroidism
MRI brain and pituitary
Other hormonal evaluation
Typical reference ranges for Serum Thyroid Hormones and TSH
Reference ranges may vary according to laboratory
|
Hormone |
Serum Levels |
|
TSH Free T4 T4 Free T3 T3 |
0.2-5.0 uIU/ml 0.8-2.0 ng/dL 4.5-12.5 ug/dL 1.4-4.4 pg/ml 86-186 ng/dL |
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Early diagnosis can be a major step forward in the treatment of hypothyroidism. |