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 Table of Contents  
Year : 2019  |  Volume : 6  |  Issue : 2  |  Page : 141-146

Low T3 syndrome is a predominant thyroid dysfunction among coronary heart disease patients: an Egyptian angiographic study

Department of Critical Care, Faculty of Medicine, Cairo University, Cairo, Egypt

Date of Submission30-Apr-2018
Date of Acceptance17-Dec-2018
Date of Web Publication12-Jun-2019

Correspondence Address:
Nora I Abbas
Department of Critical Care, Faculty of Medicine, Kasr el Ainy hospital Al-Saray Street, Cairo University, El Manial Cairo
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/roaic.roaic_38_18

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Background Cardiovascular diseases are the most common cause of mortality, primarily affecting older adults. Although the established risk factors explain most cardiac risks, alternative biochemical markers may have an assisting diagnostic role in identifying those at risk for a clinical cardiovascular event, among the abnormal thyroid gland profiles.
Aim We aimed to investigate the cardiovascular risk of thyroid profile abnormalities among patients with clinical coronary heart disease (CHD) confirmed by coronary angiography (CA).
Patients and methods An observational, prospective case–control study. Ninety cases participated in the study. They were divided into two groups: Group I (n=60) CHD patients were diagnosed by percutaneous (CA) and group II (30 participants) with negative diagnostic workup for CHD who were enrolled as the control group or (non-CHD group). Thyroid hormones profiles were withdrawn from both groups.
Results Group I (CHD patients proved by CA) had statistically significant higher age (55.18±12.303 vs. 48.73±13.014 years, P=0.024), blood glucose (207.55±74.186 mg%; P=0.002), blood urea (37.65±12.658 vs. 28.97±9.152 mg%, P=0.001), and cholesterol (246.67+99.348 vs. 199.67±47.593 mg%, P=0.003). T3 levels are significantly lower in group I (2.094±0.971 vs. 2.73+0.7221 pg/ml, P=0.002).
Conclusion Our results concluded that low T3 syndrome is the predominant thyroid dysfunction in CHD patients who underwent a CA.

Keywords: coronary angiography, coronary heart diseases, low T3 syndrome, thyroid dysfunction, Body

How to cite this article:
Effat H, Abbas NI. Low T3 syndrome is a predominant thyroid dysfunction among coronary heart disease patients: an Egyptian angiographic study. Res Opin Anesth Intensive Care 2019;6:141-6

How to cite this URL:
Effat H, Abbas NI. Low T3 syndrome is a predominant thyroid dysfunction among coronary heart disease patients: an Egyptian angiographic study. Res Opin Anesth Intensive Care [serial online] 2019 [cited 2019 Oct 14];6:141-6. Available from: http://www.roaic.eg.net/text.asp?2019/6/2/141/260144

  Introduction Top

Thyroid profile disorders are implicated in many cardiovascular diseases (CVD) which are the most common cause of mortality [1].

  Aim Top

To detect the cardiovascular risk of thyroid profile abnormalities among patients with coronary heart disease (CHD) admitted to the critical care department of Cairo University Hospital between 1 January 2013 and 1 January 2014 and who were subjected to coronary angiography (CA).

  Patients and methods Top

An observational prospective case–control study. Ninety cases participated in the study, who were divided into two groups. Group I includes 60 CHD patients proved by percutaneous CA and Group II included 30 participants who were admitted with chest pain suspicious of cardiac origin, however with negative diagnostic workup including CA for CHD who were enrolled as the control group or the non-CHD group. Demographic data, family history of ischemic heart disease (IHD), lifestyle, current smoking, and current pharmacotherapy were obtained. Height and weight were measured to calculate BMI. Routine laboratory samples in addition to thyroid hormones profile were withdrawn.

All participants in both groups were subjected to free thyroxine (T4), 3, 5, 3′-triiodothyronine (T3), and thyroid-stimulating hormone (TSH) levels estimation in addition to thorough clinical examination including height and weight to calculate BMI as weight divided by height squared.

Sitting systolic and diastolic blood pressures were measured after 5 min rest on the right arm, using standard mercury sphygmomanometers. A standard 12-lead ECG and echocardiogram were performed. Family history of CHD and major risk factors for CVD such as smoking states, hypercholesterolemia, hypertension, and diabetes mellitus were investigated.

Any patient with a previous history of thyroid disease or past or present amiodarone (cordarone) drug intake as well as participants taking thyroid hormone preparations, antithyroid drugs, and corticosteroids because of influence on TSH levels was excluded from the study.

All procedures were done with good clinical practices. Informed oral consent was obtained from all participants as they were clinically indicated for CA.

Interventional cardiologist and clinical pathology laboratory physicians were blinded to laboratory data and CA results, respectively.

The statistical paragraph in material and methods: data were statistically described in terms of mean±SD, range or frequencies (number of cases), and percentages when appropriate. Comparison of numerical variables between the study groups was done using Student’s t-test for independent samples. For comparing categorical data, χ2 test was performed. Exact test was used instead when the expected frequency is less than 5. P values less than 0.05 were considered statistically significant. All statistical calculations were done using the computer program SPSS (Statistical Package for the Social Sciences; SPSS Inc., Chicago, Illinois, USA) version 15 for Microsoft Windows.

  Results Top

Group I (the CHD group) of 60 patients had a mean age of 55.18±12.303 years, while in the non-CHD group the mean age was 48.73±13.014 years (P=0.024*).

Fifty-seven (57) participants in the study were men (63% of the total sample) and 33 participants were women (37% overall sample).

In group I, 36 participants were men (60%) and 24 (40%) were women while in group II 21 (70%) participants were men and nine (30%) were women without significant difference between the two groups (P=0.353).

Group I included 28 (47%) smokers while group II included 17 (57%) smokers without significant difference between the two groups (P=0.731).

Also, no significant differences were detected between the two groups as regards positive family history (positive FH) for IHD or history of weekly physical activity (P=0.75 and 0.188, respectively).

On the other hand, 78 participants (87% of the total sample) had positive ECG findings suggestive of CHD whereas all the participants in group I had these ECG changes versus only 60% of group II (P=0.000) ([Table 1]).
Table 1 Patient’ characteristics as regards family history for ischemic heart disease and history of weekly physical activity, positive ECG findings, and metabolic syndrome criteria in each group

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The occurrence of metabolic syndrome showed a highly statistically significant difference between both groups; 30 participants (33% of the total sample) had positive metabolic syndrome (43% of the participants in group II versus 13% of participants in group II) (P<0.05).

Group I showed higher blood glucose levels compared with group II with highly statistically significant difference (the mean blood glucose level was 207.55±74.186 vs. 167±46.398 mg% in group II with a P value of 0.002).

Blood urea levels in group I 37.65±12.658 mg% was significantly higher than in group II 28.97±9.152 mg% (P=0.001). Similarly, the total cholesterol level was significantly higher in group I 246.67±99.348 mg% than in group II 199.67±47.596 mg% (P=0.003).

BMI showed no significant differences between the two groups: 29.57±5.192 kg/m2 in group I versus 28.47±4.674 kg/m2 in group II with a P value of 0.331.

The thyroid function results analysis showed free T3 level for group I (CHD group) was 2.094±0.971 versus 2.73±0.7221 pg/ml for group II (non-CHD group) with a P value of 0.002. Free T4 level showed a significant difference between group I (1.22±0.2892 ng/l) compared with group II (1.117±0.2245 ng/l) with a P value of 0.09. Finally, the TSH level did not show any significant difference between group I (3.462±2.3536) and group II (3.392±1.4706 pg/ml) (P=0.883) ([Table 2]).
Table 2 Laboratory investigations including thyroid profile

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  Discussion Top

Although our study was of a specific population, to the authors’ knowledge this is the first study aimed at estimating the prevalence of low T3 syndrome in Egyptian patients referred for cardiology consultation and CA.

Group I (CHD group) patients had significantly higher age than group II. Age is, by far, one of the most powerful CHD risk factors. The highest incidence of ACS is found around the fifth and sixth decades of life [2],[3]. Even though, a quarter of ACS patients are older than 75 years, and a similar proportion are younger than 55 years. An observational Spanish study reported that 36% of patients were younger than 45 years [3].

The higher CHD prevalence among men increases in younger people and tends to be equal in the older age group like the case in our patients [2],[4],[5],[6].

No statistically significant differences were detected between the two groups as regards a positive family history (positive FH) for IHD which can be explained by the fact that FH is more important in the younger age group [7],[8],[9].

In addition, Only FH of premature CHD (male first-degree relatives aged <55 years and female first-degree relatives aged <65 years) is more important as it increases the risk by a factor of ∼1.5 that increases CHD risk [10].

There was presence of positive ECGs findings for IHD in all group I patients versus 60% of group II patients, P value less than 0.001.

Abnormalities in the baseline ECG are strongly associated with subsequent all-cause CVD, and CHD mortality. The predictive value was similar for men and women [11].

In addition, abnormalities in the 12-lead ECG are often used to localize the anatomic site of myocardial infarction and ischemia in CHD patients [12],[13],[14].

A very high statistically significant difference was found between both groups as regards fulfillment of the metabolic syndrome criteria as 30 participants (33% of the total sample) had metabolic syndrome, but when both groups were compared, 43% of group I patients had a positive occurrence of the metabolic syndrome versus only 13% in group II with a P value of 0.004.

The metabolic syndrome was associated with a twofold increase in cardiovascular outcomes and a 1.5-fold increase in all-cause mortality in two recent meta-analyses [15],[16].

Group I showed a high statistically significant difference in blood glucose level when compared with group II with a P value of 0.002.

Blood urea in group I was higher than in group II (P<0.001).

R-CHA2DS2VASc, based on the CHA2DS2VASc score with few modifications [addition of (glomerular filtration rate and urea), performance of a revascularization procedure and history of atrial fibrillation] predicted ischemic stroke and all-cause mortality during the follow-up of MI patients discharged alive [17]. Also, latent renal failure was a risk factor for sudden deaths due to IHD [18].

Group I had higher total cholesterol levels compared with group II.

We did not find any statistically significant difference between BMI in both groups (P=0.331).

A systematic review and meta-analysis of 97 studies showed that only severe obesity was associated with an increased risk of death from all causes, but not lesser amounts of excess weight [19].

Euthyroid sick syndrome (ESS) is the term used to describe thyroid hormonal changes in critically ill patients due to nonthyroidal illness. Low T3 is the earliest manifestation (low T3 syndrome) followed by low T4 and finally low TSH, indicating a continuum of changes in the spectrum [20],[21].

Lower T3 syndrome involves (34 patients, 5.84%) SCH (28 patients, 4.81%) and clinical hypothyroidism (14 patients, 2.41%) in a study including 582 hospitalized STEMI patients [22]. The lower FT3 level correlates with higher levels of cardiac markers CK-MB, cTns, and CRP as well as lower left ventricular ejection fraction (LVEF). The authors concluded that hypothyroidism may be a predictor for myocardial injury in STEMI. No significant correlation was found between other thyroid parameters (TSH, FT4) and cardiac markers.

A recent study involved 1752 patients who were admitted for CA and were classified according to their thyroid profile into four groups: euthyroidism (60%), low T3 syndrome (28%), hypothyroidism (10%), and hyperthyroidism (2%). The authors reported that thyroid dysfunction is frequent in patients who perform a CA, with low T3 syndrome as the predominant feature [23].

However, the high level of serum TSH is associated with multivessel disease, in 344 angina patients who underwent elective CA. It was not the determinant of CAD in patients with normal thyroid function while age, diabetes, creatinine, and smoking were independent predictors [24].

Higher serum TSH concentrations were associated with increased severity of coronary atherosclerosis in CAD patients. When the patients were grouped into three subsets according to their serum-free T3 levels (<2.79, 2.8–3.09, and ±3.1 pg/ml), the prevalence of CAD scores 2 and 3 was significantly higher in the subset of patients with low serum-free T3 levels (48.5%) than in the subsets of patients with medium or high T3 concentrations (32.25 and 25%, respectively, P<0.05) [25].

Although SCH was detected in 60% of 187 CHD patients, the low T3 syndrome was detected particularly in arrhythmic CHD (where the T3 was significantly lower, the serum level of T4 was normal and even increased and normal concentrations of TTG) [26].

FT3 levels were inversely correlated to the presence of CAD in 1047 clinically and biochemically euthyroid patients who underwent CA for suspected CAD; in addition, low T3 syndrome conferred an independent adverse prognostic factor for cardiac mortality [27].

Pimentel showed that of the 70 hospitalized ACS patients, 13 (18.6%) had ‘ESS’, a condition characterized by decreased serum T3 and/or free T3, increased serum reverse T3 (rT3), plus normal serum TSH, T4, and free T4. ESS was associated with poorer prognosis in ACS patients [1].Serum FT3 concentration is inversely correlated with the severity of CAD in euthyroid patients referred for CA. Serum FT3 concentrations also correlate with the Gensini score and independently predict the severity of CAD [28].

Low serum T3 levels seem also to have a poor prognosis in hospitalized cardiac patients and in those with congestive heart failure [29],[30]; either low serum T4 or low T3 has been associated with dismal outcomes following bone marrow transplantation [31]. Such findings called for substantial discussion of thyroid hormone treatment indication and, if so, with which hormone.

The available evidence to date on the treatment of SES patients, albeit mostly based on studies with small patient numbers, have failed to show any benefit of thyroid hormone replacement, although no clear side effects were detected either [32],[33],[34],[35],[36].

Thyroid profile samples were withdrawn just before the CA procedure. The iodine contrast media use can cause a small but significant decrease in fT4 and an increase in TSH which peaks on day 3 and depends on the preexisting thyroid function [37].


The limitation of this study is its small patient number. A larger sample size could lead to better and more validated statistical analysis results.

This was not a longitudinal study; it does not give follow-up information on the clinical course of these patients. The absence of angiographically documented lesions is not the same as the absence of cardiovascular risk, since it is known that insignificant lesions are mainly responsible for coronary events.

  Conclusion Top

Age, blood glucose, blood urea, cholesterol levels, and low T3 levels were significant predictors of angiographically documented CAD. Low T3 syndrome is the most common thyroid dysfunction among CHD patients who perform a CA. We recommend further studies to document the accurate prevalence of low T3 syndrome among CHD patients as well as to detect whether thyroxin (T4) supplementation would improve the outcome or not.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Table 1], [Table 2]


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