Schilddrüse Klein — Small Thyroid Panel

Core thyroid function panel measuring fT3, fT4, and TSH — the three markers needed to assess both thyroid hormone production and pituitary feedback. More informative than TSH alone for detecting subclinical thyroid states.

This panel measures the three primary thyroid function markers that together provide a complete picture of the hypothalamic-pituitary-thyroid axis. TSH alone can identify overt hypo- or hyperthyroidism, but the addition of free T3 and free T4 enables detection and classification of subclinical states that TSH screening misses or mischaracterises. TSH (thyroid-stimulating hormone) from the anterior pituitary is the most sensitive single marker for primary thyroid dysfunction. It rises in response to falling thyroid hormone levels and is suppressed when thyroid hormone is excessive. The reference range is approximately 0.4-4.0 mIU/L, though evidence suggests the optimal range for most adults is 0.5-2.5 mIU/L. Free T4 (thyroxine) is the predominant circulating thyroid hormone and the direct product of the thyroid gland. Only the free (unbound) fraction is metabolically active — total T4 is influenced by binding protein changes from pregnancy, oral contraceptives, liver disease, and genetic variation. Free T4 is the first marker to change in central (secondary) hypothyroidism, where TSH may be misleadingly normal. Free T3 (triiodothyronine) is the biologically active thyroid hormone, primarily produced by peripheral conversion of T4 via deiodinase enzymes. Discordant T3 and T4 levels can identify conversion disorders — for example, selenium deficiency impairs T4-to-T3 conversion and produces a pattern of normal T4 with low T3. This is also the pattern seen in non-thyroidal illness (sick euthyroid syndrome) during acute medical illness. The combination of all three markers allows classification into distinct clinical patterns: elevated TSH with low fT4 confirms primary hypothyroidism; suppressed TSH with elevated fT3 and/or fT4 indicates hyperthyroidism; mildly elevated TSH with normal free hormones identifies subclinical hypothyroidism. If autoimmune thyroid disease is suspected, the Schilddruese Gross panel adds TPO antibodies and TSH receptor antibodies for aetiological classification.