Analysis index

1 ml serum

Adults: 0,7 – 1,5 ng/dl

Children:

Up to 15 days:             1,05 ng/dl – 3,21 ng/dl

15 days – 30 days:        0,68 ng/dl – 2,53 ng/dl
30 days – 1 year:          0,89 ng/dl – 1,7 ng/dl
1 year – 19 years:         0,89 ng/dl – 1,37 ng/dl

Only utilizable in connection with the evaluation of TSH for the assessment of the thyroid function.

Exceptions:      

• Progress checks of secondary (hypophyseal/hypothalamic) hypothyroidism under substitution treatment
• Checks of thyreostatic therapy in case of autoimmune thyropathy of the Basedow type (TSH levels not usable for up to 1 year)

T4 is produced in the thyroid and deiodized in the peripheral tissues by deiodinases to T3, which is the actual active form. Slightly elevated levels may be measured when receiving L-thyroxin substitution in the morning with blood extraction directly after the last dose, without an actual overdose being present. Lower levels may be seen in both primary and secondary hypothyroidism as well as in low T3-low T4-syndrome.