Thyroid function test interpretation, here is how

Thyroid function tests are often required to be interpreted in clinical practice :

In addition it is extremely important to identify hypothyroidism in

Pregnancy and in Infancy to prevent mental retardation in the newborn

Today let us revise how to interpret thyroid function tests:

Step 1 :First choose TSH,

Step 2: Free T4 or index,

Step 3: Radioactive Iodine uptake (RAIU)

See the number. Is it low, normal or high?

A) TSH high and FT4 low

= PRIMARY HYPOTHYROIDISM

B)TSH low and FT4 LOW

= SECONDARY HYPOTHYROIDISM( Pituitary)

if TRH low (Hypothalamus)

C)TSH high FT4 normal

= SUBCLINICAL HYPOTHYROIDISM

D))TSH high and FT4 HIGH

= PITUITARY HYPERTHYROID (TUMOR)

E)TSH low and FT4 normal

= SUBCLINICAL THYROTOXICOSIS

F)TSH low FT4 high, diffuse RAIU +TSI & Anti-TSH-receptor Ab.

=GRAVE’S DISEASE

G)TSH low and FT4 high, focal RAIU= ADENOMA

H)TSH high and FT4 LOW + Anti-thyroglobulin ab.+ Anti TPO

= HASHIMOTO’S THYROIDITIS

I) FT4 NORMAL and low T3 + rT3 high+TBG low

= SICK EUTHYROID .

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