We have located links that may give you full text access.
Clinical Trial
English Abstract
Journal Article
[Effects of chronic subclinical hyperthyroidism from levothyroxine on cardiac morphology and function].
BACKGROUND: Thyroid hormones greatly affect the cardiovascular system. Although the effects of overt hyperthyroidism on the cardiovascular system have been diffusely studied, only in the last years the effects of subclinical hyperthyroidism on the heart have been investigated. Subclinical hyperthyroidism is a symptomatic or asymptomatic condition with an absent response of thyrotropin (TSH) to thyrotropin-releasing hormone in the presence of normal serum levels of thyroid hormones for the general population, though supraoptimal for the individual. The more frequent causes of endogenous subclinical hyperthyroidism are multinodular goiter, toxic, adenoma and Graves's disease, whereas the exogenous causes are induced by levothyroxine (LT4) therapy used to suppress TSH in patients with nontoxic goiter and differentiated thyroid cancer. This paper reports our experience derived from the study of 60 patients with subclinical hyperthyroidism due to TSH-suppressive therapy with LT4 compared to normal subjects.
METHODS: Patients (9 males and 51 females, mean age 39 +/- 10 years) were studied by complete Doppler echocardiography, standard and 24 hour ECG Holter monitoring, exercise test with cycloergometer, and radionuclide ventriculography at rest and during fixed workload (75 W).
RESULTS: Holter monitoring showed a significant increase in mean 24 hour heart rate (80 +/- 10 vs 70 +/- 9 b/min, p < 0.001) and supraventricular arrhythmias (42 vs 12 patients, p < 0.003). Echocardiography showed an increase in left ventricular mass index (94 +/- 13 vs 80 +/- 18 g/m2, p < 0.001) due to increased septal and posterior wall thickness. At rest, echocardiographic indices of systolic function (fractional shortening and mean corrected velocity of circumferential fiber shortening) were higher in patients than in controls (fractional shortening 40 +/- 6 vs 34 +/- 4%, p < 0.001; mean corrected velocity of circumferential fiber shortening 1.23 +/- 0.17 vs 1.05 +/- 0.14 circ/s, p < 0.001), while the Doppler indices of diastolic function were significantly impaired as documented by the reduced E/A ratio (1.18 +/- 0.3 vs 1.8 +/- 0.5, p < 0.001) and the prolonged isovolumic relaxation time (94 +/- 13 vs 78 +/- 12 ms, p < 0.001). Exercise tolerance was also significantly impaired in patients with subclinical hyperthyroidism: maximal exercise time (6.4 +/- 0.7 vs 9.4 +/- 1.4 min, p < 0.001) and peak workload (81 +/- 11 vs 121 +/- 17 W, p < 0.001) were significantly reduced and radionuclide ventriculography showed a decrease in ejection fraction during exercise (from 62 +/- 7 to 53 +/- 8%, p < 0.002).
CONCLUSIONS: Persistent subclinical hyperthyroidism by TSH-suppressive doses of LT4 significantly affects heart morphology and function. Thus, we suggest that a complete suppression of TSH must be recommended only in patients with differentiated thyroid cancer, while in patients with begin thyroid disease it could be sufficient to maintain subnormal TSH levels.
METHODS: Patients (9 males and 51 females, mean age 39 +/- 10 years) were studied by complete Doppler echocardiography, standard and 24 hour ECG Holter monitoring, exercise test with cycloergometer, and radionuclide ventriculography at rest and during fixed workload (75 W).
RESULTS: Holter monitoring showed a significant increase in mean 24 hour heart rate (80 +/- 10 vs 70 +/- 9 b/min, p < 0.001) and supraventricular arrhythmias (42 vs 12 patients, p < 0.003). Echocardiography showed an increase in left ventricular mass index (94 +/- 13 vs 80 +/- 18 g/m2, p < 0.001) due to increased septal and posterior wall thickness. At rest, echocardiographic indices of systolic function (fractional shortening and mean corrected velocity of circumferential fiber shortening) were higher in patients than in controls (fractional shortening 40 +/- 6 vs 34 +/- 4%, p < 0.001; mean corrected velocity of circumferential fiber shortening 1.23 +/- 0.17 vs 1.05 +/- 0.14 circ/s, p < 0.001), while the Doppler indices of diastolic function were significantly impaired as documented by the reduced E/A ratio (1.18 +/- 0.3 vs 1.8 +/- 0.5, p < 0.001) and the prolonged isovolumic relaxation time (94 +/- 13 vs 78 +/- 12 ms, p < 0.001). Exercise tolerance was also significantly impaired in patients with subclinical hyperthyroidism: maximal exercise time (6.4 +/- 0.7 vs 9.4 +/- 1.4 min, p < 0.001) and peak workload (81 +/- 11 vs 121 +/- 17 W, p < 0.001) were significantly reduced and radionuclide ventriculography showed a decrease in ejection fraction during exercise (from 62 +/- 7 to 53 +/- 8%, p < 0.002).
CONCLUSIONS: Persistent subclinical hyperthyroidism by TSH-suppressive doses of LT4 significantly affects heart morphology and function. Thus, we suggest that a complete suppression of TSH must be recommended only in patients with differentiated thyroid cancer, while in patients with begin thyroid disease it could be sufficient to maintain subnormal TSH levels.
Full text links
Related Resources
Trending Papers
Interstitial Lung Disease: A Review.JAMA 2024 April 23
Review article: Recent advances in ascites and acute kidney injury management in cirrhosis.Alimentary Pharmacology & Therapeutics 2024 March 26
Executive Summary: State-of-the-Art Review: Unintended Consequences: Risk of Opportunistic Infections Associated with Long-term Glucocorticoid Therapies in Adults.Clinical Infectious Diseases 2024 April 11
Clinical practice guidelines on the management of status epilepticus in adults: A systematic review.Epilepsia 2024 April 13
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app
All material on this website is protected by copyright, Copyright © 1994-2024 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.
By using this service, you agree to our terms of use and privacy policy.
Your Privacy Choices
You can now claim free CME credits for this literature searchClaim now
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app