Troponiinin

Troponin is a regulatory protein complex found in striated muscle that controls contraction in response to calcium. It consists of three subunits: troponin C, which binds calcium; troponin I, the inhibitory subunit; and troponin T, which anchors the complex to tropomyosin on actin filaments. In cardiac muscle, there are cardiac-specific isoforms of troponin I and troponin T (cTnI and cTnT). The complex modulates the exposure of myosin-binding sites on actin, thereby regulating the interaction between actin and myosin during contraction.

Cardiac troponins are released into the bloodstream when cardiac myocytes are damaged, making them important biomarkers for myocardial injury. Measurement of cardiac troponins in a patient with chest pain or other symptoms of ischemia is a central component of diagnosing acute coronary syndromes. High-sensitivity assays can detect very low concentrations and allow earlier detection. Clinically, an elevated troponin level is defined relative to the assay’s reference limit, often based on the 99th percentile of a healthy population; however, interpretation requires serial measurements to observe a rise or fall in concentration, in conjunction with clinical assessment, ECG findings, and imaging studies. Troponin elevations can also occur in non-ischemic conditions such as heart failure, myocarditis, renal failure, pulmonary embolism, sepsis, and after strenuous exercise.

Limitations include assay variability and the fact that troponin elevation indicates myocardial injury but not its cause. Therefore, troponin results are interpreted within the broader clinical context and may be repeated over time to inform diagnosis and prognosis.