Examination for thyroid diseases

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Indicators of thyroid dysfunction

Thyroid hormone feedback

TSH in serum

• Its concentration is inversely proportional to the concentration of [[T₄]] ,
  • assuming normal function of the hypothalamic-pituitary axis reflects the level of T 4 ,
• Significantly increased: primary hypothyroidism,
• Sometimes produced modified - you can also find
• The method of first choice in case of suspected primary hypothyroidism or hyperthyroidism,
• Monitoring of T₄ substitution therapy ,
• Is investigated in hypercholesterolemia and hyperprolactinemia.

Function test with TRH

• Reflects TSH secretion
• in central hypothyroidism, in TSH-producing tumors.

Total thyroxine (TT4) and free (FT4) in serum

• Current secretion indicators
• FT4 indicates the availability of the hormone by tissues
• 

  Thyroxine
  free thyroxin index – FTI

$FTI={\frac {concentration\ T4\cdot \%T3-Uptake}{100}}\$

• Prior to the treatment of hyperthyroidism, TSH secretion may still be suppressed in the long term.

Triiodothyronine total (TT3) and free (FT3) in serum

• 

  Triiodothyronine
  High levels of T₃ autonomic hyperactivity of the gland
• Indications - examination of hyperthyroidism, severity of primary hypothyroidism, differential diagnosis of low TSH levels.

Reverse T₃ (RT3)

• Indirect indicator of T4 to T3 conversion,
• Examination of unknown causes of low TT3 or TT4.

Serum Thyroglobulin (TG)

• Indicator of TG release from the active, inflammatory or tumor gland,
• Follow-up of patients after thyroidectomy for differentiated ca as a tumor marker - diagnosis of relapse (increasing TG).

α-subunit of hCG

• In general, it detects the formation of molecules with this subunit - even TSH.

Calcitonin, serum thyrocalcitonin

• Thyroid gland C-cell secretory activity indicator ,
• In the diagnosis of medullary tumors.

Disorders of thyroid hormone transport

Serum thyroxine binding globulin (TBG)

• Quantitatively the most important carrier,
• High values: genetically, in pregnancy, contraception,
• Low concentrations: malnutrition, malabsorption, hepatic synthesis disorders,
• We examine at T3 and T4 values ​​that do not correlate with the clinical condition.

Prealbumin, transthyretin in serum

• The second most important carrier.

Binding capacity of transport proteins, T-uptake

• Significance and indications as for TBG, saturate the serum sample with a known concentration of T3 and determine the unbound fraction.

Indicators of autoimmune diseases of the thyroid gland

Thyroperoxidase Antibodies (Thyreoperoxidase Antibodies, TPOAb)

• Formerly described as antimicrosomal,
• Reveal the presence of an autoimmune process, the possible risk of dysfunction,
• Indications: goiter of unknown etiology, differential diagnosis of hyperthyroidism,
• Postpartum risk screening.

Anti-thyroglobulin antibodies

• They reveal the autoimmune process, they can explain incorrect results of TGB determination,
• Monitoring of differentiated thyroid carcinomas.

Antibodies to TSH receptors

• They can either stimulate or inhibit,
• Risk of developing Graves' disease, risk of endocrine ophthalmopathy,
• Differential diagnosis of hyperthyroidism.

Links

Related articles

• Thyroid gland
• Thyroid hormones
• Hyperthyroidism
• Hypothyroidism
• Examination of thyroid function
• Thyroid disease
• Radionuclide examinations of the thyroid gland
• Symptomatic mental disorders in endocrinopathies

References

• SCHNEIDERKA, Petr, et al. Chapters from clinical biochemistry. 2nd edition. Prague: Karolinum, 2004. ISBN 80-246-0678-X.

Source

ws:Vyšetření u chorob štítné žlázy