Thyroid function tests
As a test of thyroid function laboratory methods are referred to the review of thyroid function.
Thyroid function tests are performed in suspected hyperthyroidism ( overactive thyroid ) or hypothyroidism ( underactive thyroid ) or for therapy control of a substitution with thyroid hormones. Even in situations that may be associated with thyroid disease, such as atrial fibrillation or anxiety disorders, they can contribute useful information.
Normal thyroid function tests include provisions of TSH and / or peripheral thyroid hormones such as thyroxine (T4 ) and triiodothyronine (T3).
- 3.1 Thyroid hormone uptake
- 3.2 Other binding assays
- 4.1 Free T4 index
Thyroid hormones
Thyrotropin
The thyrotropin ( TSH ) levels are elevated in the case of primary hypothyroidism and decreased in the case of primary hyperthyroidism.
Total thyroxine
Total thyroxine ( total T4 ) is generally increased in the case of hyperthyroidism and decreased in hypothyroidism. Due to increased TBG levels it is usually slightly increased in pregnancy.
Reference range:
Free thyroxine
Free Thyroxine (Free T4) is usually increased in hyperthyroidism and decreased in the case of hypothyroidism.
Reference range:
Total triiodothyronine
Total triiodothyronine ( total T3 ) is generally increased in the case of hyperthyroidism and decreased in hypothyroidism.
Reference range:
Free triiodothyronine
Free Triiodothyronine (Free T3) is generally increased in hyperthyroidism and decreased in the case of hypothyroidism.
Reference range:
Survey
Calculated indices of free hormone levels
- Free T4 index ( FT4I )
- Free T3 index ( FT3I )
Transport proteins
An increase in the level of Thyroxinbindendem globulin ( TBG), increases the levels of total thyroxine and triiodothyronine overall, without the production of thyroid hormones would be really risen. The reference range is 12-30 mg / l
For thyroglobulin, the reference range 1.5-30 pmol / l or 1-20 is ug / l
Other binding proteins transthyretin ( thyroxine-binding prealbumin ), and albumin.
Diagnosis of protein binding function
Thyroid hormone uptake
Thyroid hormone uptake (T4 - T3 uptake or uptake) is a measure of the unbound (that is not saturated with thyroid hormones ), thyroxine binding globulin in blood plasma. The unsaturated TBG increases with decreased thyroid hormone levels. Despite the name, T3 -uptake, it is not derived from T3 levels.
Reference range:
Other binding assays
- Thyroid hormone binding ratio (Thyroid hormone binding ratio, THBR )
- Thyroxine - binding index ( TBI)
Mixed parameters
Free T4 index
The free thyroxine index (FTI or T7 ) results from the multiplication of the total T4 levels with the T3 uptake. The FTI is seen in disorders of plasma protein binding of Jodothyroninen as relatively reliable.
The FTI is increased in the case of hyperthyroidism and decreased in hypothyroidism.
Reference range:
Structural parameters
For specific questions, such as for the diagnosis of euthyroid sick syndrome or secondary hypothyroidism supply calculated structural parameters, the constant properties of the Schilddrüsenhomöostase describe useful additional information.
The secretion of the thyroid gland (GT, also called SPINA - GT) defines the maximum amount of thyroxine stimulated, which may distribute the thyroid gland in a second. GT is increased in the case of hyperthyroidism and reduced in hypothyroidism. Your reference range is 1.41 to 8.67 pmol / s
The sum activity of peripheral deiodinases (GD, also SPINA -GD) correlated with the TSH levels. It is reduced in the case of a Non- thyroidal illness syndrome with Hypodejodierung. Your reference range is 20-40 nmol / s
With the help of the introduced of Jostel TSH index ( TSHI ) and based on standardized TSH index ( sTSHI ) the thyrotropic function of the pituitary can be estimated quantitatively. The reference range for the TSH index is 1.3 to 4.1.