Cardiac troponin T is not increased in patients with hypothyroidism
R Ness-Abramof1, D A Nabriski, M S Shapiro
1Endocrine Unit, Sapir Medical Center, Kfar Saba, Israel. rosane-abramof.ness@clalit.org.il
Insights
Hypothyroidism commonly elevates creatine kinase (CK) but not cardiac troponin T (cTnT). This study confirms cTnT is a reliable cardiac injury marker in hypothyroid patients, even with elevated CK levels.
Area of Science:
- Endocrinology
- Cardiology
- Biochemistry
Background:
- Hypothyroidism is frequently associated with elevated creatine kinase (CK) levels.
- The exact mechanisms behind increased CK in hypothyroidism, including production, cell permeability, and clearance, are debated.
- Cardiac troponins are highly specific biomarkers for detecting cardiac injury.
Purpose of the Study:
- To investigate cardiac troponin T (cTnT) levels in patients diagnosed with primary hypothyroidism.
- To assess the reliability of cTnT as a cardiac injury marker in the context of hypothyroidism.
Main Methods:
- Evaluated 25 patients with primary hypothyroidism (TSH >30 mU/L, low FT(4)).
- Measured thyrotropin (TSH), free thyroxine (FT(4)), creatine kinase (CK), CK-MB, and cardiac troponin T (cTnT).
Main Results:
- Elevated CK levels were observed in 14 out of 25 patients.
- CK-MB was elevated in 4 patients (16%).
- All 25 patients exhibited normal cardiac troponin T (cTnT) levels (< 0.01 ng/mL).
Conclusions:
- Increased CK and CK-MB are common findings in hypothyroidism.
- Cardiac troponin T (cTnT) levels remain normal in hypothyroid patients, irrespective of CK or CK-MB elevations.
- cTnT is a dependable biomarker for assessing cardiac injury in individuals with hypothyroidism.
Abstract:
Patients with hypothyroidism often have increased creatine kinase (CK) levels. It is possible that there is increased production of CK, but other mechanisms, such as an increased cell membrane permeability or decreased enzyme clearance were also proposed. Recently, troponins T and I have been extensively studied because of their cardiac specificity. Cardiac troponins are sensitive and specific markers of cardiac injury. The objective of the study was to measure cardiac troponin T (cTnT) levels in patients with hypothyroidism. Twenty-five patients with primary hypothyroidism were evaluated (thyroid-stimulating hormone (TSH) >30 mU/L and low FT(4)). In all patients thyrotropin (TSH), free thyroxine (FT(4)), CK, CK-MB and cTnT were measured.There were 3 men and 22 women with a mean age of 47.5 +/- 12.4 years. TSH levels ranged from 31 to 75 mIU/L and mean FT(4) levels were 4.5 +/- 1.9 pmol/L. CK was normal in 11 patients and increased in 14. CK levels ranged between 86 and 1221 U/L (normal levels <170 in women, <195 in men) with a mean of 322 U/L +/- 279. CK-MB was increased in 4 patients (16%) and normal in 21. All 25 patients had normal cTnT levels, < 0.01 ng/mL (normal levels 0-0.1 microg/L). Increase in CK and its MB fraction are common in patients with hypothyroidism but cTnT levels are not, even in patients with increased CK-MB. Therefore, cTnT is a reliable marker of cardiac injury even in the hypothyroid patient.
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