I Clinical Criteria
- History taking to evaluate patients at risk
- Symptoms/signs of thyroid
hormone deficiency
- Evidence of disease/previous treatment or exposure
known to cause thyroid/pituitary/ hypothalamic failure
- Conditions associated
with increased risk of chronic autoimmune thyroiditis
II Laboratory Testing
Specific
tests
Include measurement of TSH, T4 or FT4 (Free T4), T3 or, FT4 (Free T3)
In
primary hypothyroidism
Decreased T3, T4 levels with elevated TSH or Normal
T3 low T4 and high TSH / Low T3 occurs in severe cases
In subclinical hypothyroidism
Normal
T3, T4 levels with elevated TSH levels
In central hypothyroidism
Low T3,
and T4 levels with normal or low T3, T4, 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
T4Low
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 was introduced
in 1974. This has improved the prognosis of patients with congenital hypothyroidism.
Ideally, screening should be done with T4 and TSH levels by 4th day of neonatal
life and reconfirmed by with following values FT4< 6mg/dl and TSH > 20-40
m I U /L
In case of central hypothyroidism
- MRI brain and pituitary
- Other hormonal evaluation
Typical reference ranges for Serum
Thyroid Hormones and TSH*
| TSH |
0.3 - 4.0 mu/L |
| Free T 4 |
0.7 - 2.1 ng/dL |
| T 4 |
4.0 - 11 mg/dL |
| Free T 3 |
0.2 - 6.5 ng/dL |
| T 3 |
75 - 175 ng/dL |
| *
Reference ranges may vary according to laboratory |
Early diagnosis can be
a major step forward in the treatment of hypothyroidism. In the next section we
will discuss the treatment of hypothyroidism.
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For the management of hypothyroidism |
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For the management of hyperthyroidism |
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