title: Effects of long-term thyroid hormone suppressive treatment on the cardiac functions.
abstract: Long-term effects of thyroid hormone suppressive therapy on the heart were evaluated in 45 patients by non-invasive techniques. Fifteen patients were athyreotic after surgery for differentiated thyroid cancer and 30 had diffuse or nodular goiter. Mean age of the group was 42 +/- 12 years. Twenty-four age- and sex-matched subjects were taken as controls. Mean daily dose of levothyroxine was 158 +/- 36 micrograms. Plasma thyroid stimulating hormone (TSH) levels were within normal range. Mean serum T4 and free T4 were significantly higher (p < 0.001) whereas mean serum T3 and free T3 did not differ from the control levels. Non-invasive cardiac assessment was done by a standard 12 lead electrocardiogram (ECG), ambulatory electrocardiographic (Holter) monitoring and echocardiographic study. Six patients had left ventricular hypertrophy in ECG. Holter monitoring demonstrated a higher average heart rate in patients compared to controls (86 +/- 10 vs 72 +/- 6 beats/min; p < 0.001). Supraventricular premature beats were more frequent in patients than in the control group (98% vs 60%; p < 0.06). Echocardiogram showed an increased left ventricular (LV) mass index in patient group (98 +/- 28 vs 78 +/- 16 gm/m2; p < 0.02). LV systolic function was increased with higher values of fractional shortening (40 +/- 8% vs 34 +/- 6%; p < 0.05) and rate-adjusted velocity of shortening (1.4 +/- 0.12 vs 1.02 +/- 0.16 circumferences/sec; p < 0.01). It is concluded that long-term levothyroxine suppressive therapy has significant effects on the cardiac functions.
authors.affiliation: Department of Cardiology, Institute of Nuclear Medicine and Allied Sciences, Delhi.
authors.forename: C M
authors.initials: CM
authors.lastname: Khanna
authors.forename: Y S
authors.initials: YS
authors.lastname: Dubey
authors.forename: R
authors.initials: R
authors.lastname: Shankar
authors.forename: G
authors.initials: G
authors.lastname: Kaur
mesh_terms: D000328:Adult; D001145:Arrhythmias, Cardiac / Q000139:chemically induced; D018880:Atrial Premature Complexes / Q000139:chemically induced; D016022:Case-Control Studies; D004452:Echocardiography; D004562:Electrocardiography; D015716:Electrocardiography, Ambulatory; D005260:Female; D006042:Goiter / Q000188:drug therapy; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000139:chemically induced; D008297:Male; D013964:Thyroid Neoplasms / Q000188:drug therapy; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage / Q000009:adverse effects*; D013997:Time Factors
chemical_list: D013972:Thyrotropin; D013974:Thyroxine