Objective: To characterize cardiac structure and function and cardiac autonomic control in patients with subclinical and overt hyperthyroidism. Design: Thirty patients with subclinical hyperthyroidism and 30 with overt disease were selected from patients never previously treated for endocrinological disease in the outpatient clinic of our institution. Twenty normal individuals were studied as control group. Methods: Left ventricular structure and function and cardiac autonomic control were evaluated, respectively, by two-dimensional Doppler echocardiography and by 24-h Holter recording with heart rate variability analysis. Results: Patients with overt hyperthyroidism showed greater values of left ventricular end-diastolic volume P , 0X05 and left ventricular mass P , 0X05 than patients with subclinical disease. In addition, the mean velocity of left ventricular ®bre shortening P , 0X05 and left ventricular ejection fraction P , 0X05 were greater in patients with overt hyperthyroidism than in patients with subclinical disease. No difference in any of these parameters was detectable between normal subjects and patients with subclinical disease. The isovolumic relaxation period was shorter in patients with subclinical hyperthyroidism than in control individuals P , 0X05 and in patients with overt hyperthyroidism P , 0X05. As regards cardiac autonomic control, all time and frequency domain measures decreased progressively from control individuals to patients with subclinical hyperthyroidism and those with overt disease P , 0X001. Conclusions: Thyrotoxic patients show changes in left ventricular structure and increased echocardiographic indexes of myocardial contractility, whereas the only echocardiographic feature detectable in patients with subclinical hyperthyroidism is an increased velocity of left ventricular relaxation. Cardiac parasympathetic withdrawal is evident in patients with overt hyperthyroidism and in patients with subclinical disease.

To investigate the effects of long term thyroid hormone suppressive therapy on the heart, 20 patients were evaluated by noninvasive techniques. Of them, 10 were athyreotic after surgery for differentiated thyroid cancer, and 10 had diffuse or nodular goiter. The mean age of the group was 39 +/- 11 yr. Twenty age- and sex-matched subjects served as controls. The mean dose of levothyroxine was 163 +/- 34 micrograms daily. Plasma TSH was undetectable in all patients. Mean serum T4, free T4, and sex hormone-binding globulin were significantly higher (P < 0.001), whereas mean serum T3, free T3, and osteocalcin did not differ from control levels. Cardiac evaluation consisted of a standard 12-lead electrocardiogram, an ambulatory electrocardiographic monitoring (Holter), and an echocardiographic study. Two patients showed abnormal electrocardiograms for left ventricular hypertrophy. Holter demonstrated an increase in average heart rate (84 +/- 7 vs. 70 +/- 6 beats/min; P < 0.01). Prevalence of atrial premature beats was higher in the patient group than in the control group (100% vs. 60%; P < 0.006). The echocardiogram showed an increased left ventricular mass index in the patient group (97 +/- 24 vs. 80 +/- 18 g/m2; P < 0.02). Furthermore, left ventricular systolic function was enhanced, with higher values of fractional shortening (38 +/- 7% vs. 34 +/- 4%; P < 0.05) and rate-adjusted velocity of shortening (1.2 +/- 0.13 vs. 1.05 +/- 0.14 circumferences/sec; P < 0.01). These findings indicate that long term levothyroxine therapy at suppressive doses markedly affects cardiac function.

No abstract

S UBCLINICAL HYPOTHYROIDISM (SH) is a commondisorder characterized by increased serum TSH and its response to TRH, whereas serum free T 4 (FT 4 ) and free T 3 (FT 3 ) concentrations are within the normal range for the general population (1, 2). In view of the minor thyroid hormone secretion impairment, it is predictable that metabolic and organ function indexes of SH will show only marginal alterations. Nevertheless, such changes may be clinically relevant when they affect target organs over a period of several years (3). In particular, heart and vessels are very sensitive to thyroid hormones, as cardiovascular disorders are often associated with both overt hypothyroidism and hyperthyroidism (4 -8). Several noninvasive techniques (9 -16) have been used to assess cardiac involvement in SH, but all of them provide information about left ventricular (LV) global chamber function without exploring changes occurring at the level of the regional myocardial walls.Pulsed tissue Doppler (TD) is a new noninvasive ultrasound tool that allows measurement of myocardial regional wall motion. Although standard echocardiography collects data about cardiac function either from parameters measured from the blood-myocardial boundaries or from Doppler flow, TD has the peculiarity of directly measuring velocities and time intervals of myocardium by placing a sample volume within the chosen myocardial walls. It is noteworthy that TD evaluation is performed on line during a simple echocardiographic examination by modifying filter settings and reducing velocity ranges of the standard Doppler signal (17)(18)(19).On these grounds the present study was designed to investigate myocardial regional function in SH by using pulsed TD to identify possible LV myocardial systolic and diastolic involvement in relation to a reference population of euthyroid healthy subjects. Subjects and Methods Study protocolTwenty female patients (mean age Ϯ sd, 38.5 Ϯ 12.4 yr) with newly diagnosed, untreated, autoimmune primary SH and no previous history of thyrotoxicosis were included in the study. SH was diagnosed in those cases where TSH values were above normal and associated with a supranormal response to TRH (change in TSH, Ͼ30 mU/liter) and FT 3 and FT 4 levels in the lower limit of the normal range. Only patients with TSH and thyroid hormone levels stable for at least 6 months before enrolment were included. TSH and thyroid hormones were considered stable if their variations were lower than 20% in 3 consecutive evaluations performed in the 6 months preceding the current study. Twenty female healthy subjects, recruited among the staff and relatives of medical doctors attending the present study, were included in the control group. All subjects gave informed consent, and the study was approved by the institutional ethical committee. Exclusion criteria were history of any acquired and/or congenital cardiac disease; arterial systemic hypertension; diabetes mellitus; respiratory, hematological, liver, and/or kidney diseases; pregnancy; administration of cardia...