1st-order laboratory parameters-obligatory laboratory tests.
- TSH (thyroid-stimulating hormone).
- FT3 (triiodothyronine) and fT4 (thyroxine)
- TRH-TSH test
| Primary hypothyroidism | Secondary hypothyroidism* | |
| TSH | ↑ | ↓ /normal |
| fT3, fT4 | ↓ | ↓ |
* Most common causes of sec. Hypothyroidism are tumors, trauma, and hemorrhage in the pituitary gland area.
| Latent hypothyroidism | Manifest hypothyroidism | |
| TSH | ↑ | ↑ |
| fT3, fT4 | (still) within normal range | ↓ |
| Hypothyroid coma (myxedema coma) | ||
| Primary hypothyroidism | Secondary hypothyroidism | |
| TSH | ↑↑ | ↑↑ |
| fT3, fT4 | ↓↓↓ | inadequately normal or reduced |
Note in pregnancy:In pregnant women, T4 levels generally drop to levels of circa 0.5 ng/dl from 12 weeks of gestation (= isolated hypothyroxinemia). This is caused by a relative iodine deficiency.Isolated hypothyroxinemia is a special form of hypothyroidism. 2nd order laboratory parameters – depending on the results of the medical history, physical examination, etc. – for differential diagnostic clarification.
- TPO antibody (synonyms: thyroid peroxidase, MAK) – for diagnosis of autoimmune thyroid diseases such as Hashimoto’s thyroiditis (autoimmune thyroiditis); initially with increased secretion of thyroid hormones, later with gradual transition to hypothyroidism. MACs 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.
- Thyroglobulin antibodies (Tg antibodies; TAK) – for the diagnosis of autoimmune thyroid diseases such as Hashimoto’s thyroiditis.
- TRAK (TSH receptor antibody; auto-Ak against TSH receptor), TAK (auto-Ag (IgG) against thyroglobulin), A-TPO (anti-thyrosine peroxidase-Ak) – because of autoimmune thyroiditis (autoimmune disease of the thyroid gland; initially with increased secretion of thyroid hormones (hyperthyroidism), later with gradual transition to hypothyroidism).
- Prolactin (hormone) – hypothyroidism stimulates prolactin production and secretion due to increased hypothalamic TRH formation; this can be the cause of follicle maturation disorder (egg maturation disorder) in women and can be the cause of libido disorder in men.
- Uric acid
Laboratory diagnosis of suspected hypothyroid coma (myxedema coma)
Laboratory parameters 1st order – obligatory laboratory tests.
- TSH, fT3, fT4 [primary hypothyroidism: basal TSH ↑, free thyroxine (fT4) ↓; note esp. the clinical picture: Hypothermia, neuropsychiatric symptoms, clouding of consciousness (somnolence) to coma, etc.]Note: Wg. overlapping NTIS (Non-Thyroidal-Illness-Syndrome) due to severe disease, examination of peripheral thyroid hormones is of little help, as these are lowered in the context of NTIS anyway.NTIS is characterized by three components, which can 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
- Glucose [hypoglycemia/ hypoglycemia]
- Sodium [hyponatremia (sodium deficiency)] (approximately 50% of patients with myxedema coma).
- Lactate dehydrogenase (LDH) [ ↑ ]
- Creatine kinase (CK) [ ↑ ]
- Renal parameters – urea, creatinine, cystatin C if necessary [limitation of GFR (glomerular filtration rate)].
