1st-order laboratory parameters-obligatory laboratory tests.
- TSH (thyroid-stimulating hormone) and fT3 (triiodothyronine) and fT4 (thyroxine).
- TRH-TSH test – thyroid function diagnostics.
| Primary hyperthyroidism | Secondary hyperthyroidism* | |
| TSH | ↓ | ↑ /normal |
| fT3, fT4 | ↑ | ↑ |
* The most common cause of sec. Hyperthyroidism is a tumor (adenoma).
| Latent hyperthyroidism | Manifest hyperthyroidism | |
| TSH | ↓ | ↓ |
| fT3, fT4 | (still) within normal range | ↑ |
2nd order laboratory parameters – depending on the results of the medical history, physical examination, etc. – for differential diagnostic clarification
- TSI antibodies (thyroid-stimulating antibodies) – for diagnosis of autoimmune thyroid diseases such as Graves’ disease.
- TRAK (auto-Ak against TSH receptor), TAK (auto-Ag (IgG) against thyroglobulin), A-TPO (anti-thyrosine peroxidase-Ak) [elevation of TRAK levels: high probability of immune hyperthyroidism M. Graves’ disease]
- TPO (synonyms: thyroid peroxidase, MAC) – due to autoimmune thyroiditis (autoimmune disease of the thyroid gland; initially with increased secretion of thyroid hormones, later with gradual transition to hypothyroidism – hypothyroidism)MAC are found:
- Slightly elevated in: Goiter, functional autonomy, other autoimmune diseases.
- Markedly elevated in: Hashimoto’s thyroiditis (autoimmune thyroiditis Hashimoto) (> 90%), primary myxedema, Graves’ disease (70%).
If TRAK and MAK are found, then this speaks for M. Graves.
- Serum Tg level (serum thyroglobulin level).
- Calcitonin – due togoiter maligna
- Uric acid
Pregnancy hyperthyroidism
- Normal: As a result of accelerated thyroid metabolism, there may be a nonpathologic increase in triiodothyronine (T3) and thyroxine (T4). The concentration of thyroid-stimulating hormone (TSH), on the other hand, is often reduced in pregnant women.Due to the fact that the alpha chain of HCG is identical to the alpha chain of LH, FSH, and TSH, it is explained that HCG has a thyrotropic effect. Therefore, physiologically, in the 1st trimester (third trimester), there is an increased synthesis of T4 with the consequence that the endogenous TSH level is somewhat suppressed. This thyroid function normalizes at the latest in the second trimester.
- Pathologies in pregnancy:
- FT3 + fT4 in the upper normal range = latent hyperthyroidism.
- FT3 + fT4 = manifest hyperthyroidism hyperthyroidism often accompanied by hyperemesis gravidarum
Laboratory diagnostics in old age
Laboratory diagnostics in old age provide less clear information than in younger age:
- T4 → T3 conversion is decreased in old age.
- Thyroxine requirement is decreased in old age
Thus, the level of normal values of fT3 and fT4 is lower in old age, so that even the constellation of subclinical (latent) hyperthyroidism with high-normal peripheral hormone serum levels in individual cases can mean a manifest hyperthyroid metabolic situation.
Laboratory diagnostics in suspected thyrotoxic coma
1st-order laboratory parameters-obligatory laboratory tests.
- TSH, fT3, fT4 [evidence of hyperthyroidism: suppressed TSH, free thyroxine (fT4) ↑, free triiodothyronine (fT3) ↑; note esp. the clinical picture: fever, cardiac symptoms (tachycardia; atrial fibrillation), central nervous symptoms, impaired consciousness, etc.]Note: Wg. overlapping NTIS (Non-Thyroidal Illness Syndrome) due to severe disease, peripheral thyroid hormones may be in the normal range as they are decreased in NTIS.NTIS is characterized by three components that may occur individually or in combination:
- Central hypothyroidism (thyrotropic adaptation, low-TSH syndrome).
- Impaired binding of thyroid hormones to plasma proteins.
- Decreased synthesis (formation) of T3 (triiodothyronine) with concomitant increased conversion of T4 (thyroxine) to rT3 (reverse triiodothyronine; low-T3 syndrome) and 3,5-T2 (3,5-diiodo-L-thyronine).
- Small blood count [leukocytosis or leukopenia/increased or decreased number of leukocytes (white blood cells]
- Glucose [hyperglycemia/hyperglycemia]
- Calcium [hypercalcemia/calcium excess]
- Liver parameters – alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), glutamate dehydrogenase (GLDH) and gamma-glutamyl transferase (γ-GT, gamma-GT; GGT), alkaline phosphatase, bilirubin [elevation of transaminases and/or cholestasis parameters].
Laboratory screening in the newborn (neonatal screening)
- T4 (thyroxine) from heel blood – to exclude congenital hyperthyroidism (congenital hyperthyroidism).
- TSH (thyroid-stimulating hormone) – checking thyroid function in the first year of life, as measurement of T4 in dried blood does not reliably detect all newborns [TSH ≥ 7.4 μlU/ml (= mU/l): more extensive diagnostics and regular checking of thyroid function].
