Divergent changes of serum 3,5,3'-triiodothyronine and 3,3',5'-triiodothyronine in patients with acute myocardial infarction

Value of the fT3/fT4 ratio and its combination with the GRACE risk score in predicting the prognosis in euthyroid patients with acute myocardial infarction undergoing percutaneous coronary intervention: a prospective cohort study

Background

Thyroid hormones deeply influence the cardiovascular system; however, the association between the fT3/fT4 ratio and the clinical outcome in euthyroid patients with acute myocardial infarction (AMI) undergoing percutaneous coronary intervention (PCI) is not well defined. Therefore, the present study aimed to assess the prognostic performance of the fT3/fT4 ratio in predicting the long-term prognosis in euthyroid patients with AMI undergoing PCI.

Methods

In a prospective cohort study with a 1-year follow-up, according to the clinical end point, 953 euthyroid individuals (61.0 ± 11.6; female, 25.8%) were divided into two groups: (1) the survival group (n = 915) and (2) the death group (n = 38).

Results

According to Cox regression multivariate analysis, fT4 (HR: 1.249, 95% CI: 1.053–1.480, p = 0.010) and the fT3/fT4 ratio (HR: 3.546, 95% CI: 1.705–7.377, p = 0.001) were associated with an increased risk of 1-year all-cause mortality. The prognostic performance of the fT3/fT4 ratio was similar to the Global Registry of Acute Coronary Events (GRACE) score in predicting 1-year all-cause mortality (C-statistic: z = 0.261, p = 0.794; IDI: -0.017, p = 0.452; NRI: -0.049, p = 0.766), but better than fT4 (C-statistic: z = 2.438, p = 0.015; IDI: 0.053, p = 0.002; NRI: 0.656, p < 0.001). The fT3/fT4 ratio also significantly improved the prognostic performance of the GRACE score (GRACE score vs GRACE score + fT3/fT4 ratio: C-statistic: z = 2.116, p = 0.034; IDI: 0.0415, p = 0.007; NRI: 0.614, p < 0.001).

Conclusions

In euthyroid patients with AMI undergoing PCI, the fT3/fT4 ratio was an independent predictor of 1-year all-cause mortality. Its prognostic performance was similar to the GRACE score, and also improved its prognostic performance (GRACE score vs GRACE score + fT3/fT4 ratio).

Non-selective and selective beta-1-adrenoceptor blocking agents in the treatment of hyperthyroidism

Treatment for one month with propranolol or atenolol, a selective beta-1-adrenoceptor blocking agent, was evaluated in 20 hyperthyroid patients. The patients improved to the same extent on either drug, as shown by a clinical diagnostic index. Basal metabolic rate decreased by 11% during both treatments, while it was unchanged in seven untreated hyperthyroid controls. Thyroxine concentration did not change during any treatment. During propranolol treatment T3 decreased from 4.6 to 3.9 nmol/l, while no changes were observed during atenolol treatment or in the control group. No significant changes were seen in free T4, free T3 or rT3 concentrations on any treatment, although free T3 was observed to decrease slightly during propranolol treatment. Thus, the improvement of the clinical symptoms of hyperthyroidism cannot be explained by diminished thyroid hormone concentrations in serum, since the reduction was small during propranolol and absent during atenolol treatment.

The influence of endogenous cortisol on the peripheral conversion of thyroxine in patients with acute myocardial infarction

A study was performed to elucidate whether endogenous cortisol, as previously suggested, could be responsible for the decreased T3 levels seen in euthyroid patients with acute myocardial infarction. Levels of these hormones as well as levels of T4 and reverse-T3 were monitored in 31 consecutive patients admitted to the Coronary Care Unit with symptoms of precordial pain or with acute arrhythmias. Sixteen of the patients had proven myocardial infarction, the remaining 15 were used as a control group. The results demonstrated that a reduction of T3 levels was seen in the infarction group without evidence of a statistically significant difference between the daily mean cortisol levels. No significant difference could be observed in T4 or reverse-T3 levels in the two groups or in T3 levels in the control group. It is concluded that the decrease in T3 levels is not a consequence of the increased levels of endogenous cortisol.

Euthyroid sick syndrome in acute ischemic syndromes

The purposes of this study were to assess the occurrence of euthyroid sick syndrome in patients with acute myocardial infarction (AMI) or unstable angina (UA), and the relationship with beta-blocker or thrombolytic therapy. Plasma triiodothyronine (T3), reverse T3 (rT3), free T3 (FT3), thyroxine (T4), free T4 (FT4), thyroid-stimulating hormone (TSH), thyroxine-binding globulin (TBG), and albumin (ALB) levels were determined in 95 patients (59 males, 36 females, aged 58.4+/-9) with AMI and 19 patients (13 males, 6 females aged 54.7+/-12.3) with UA for 5 consecutive days from the onset of the acute syndrome and 1 month later. Patients were divided according to beta-blocker therapy and thrombolytic therapy. There was a significant T3 decrease and rT3 increase in all patients during the first 5 days following admission (p < 0.05). FT3 and FT4 remained unchanged during the study. In patients with complicated infarctions, the rT3 increase and the T3 decrease were significantly greater compared to those with uncomplicated infarctions (p<0.03). TSH, T4, TBG, and ALB were significantly (p<0.05) decreased only in complicated infarctions. No differences were observed between patients with or without thrombolysis or patients with or without beta-blocker treatment. The apparent decrease in T3, the increase in rT3 levels and the decreased TSH and T4 levels, show clearly that the euthyroid sick syndrome (low T3) occurs not only in AMI but also in UA. In addition, these hormonal changes are not affected by beta-blocker therapy and thrombolysis does not influence the occurrence of the syndrome. The degree of T3 decrease is proportional to the severity of cardiac damage and may have a possible prognostic value.

Free thyroxine in myocardial infarction

High values for the free thyroxine fraction were found in the serum of 24 patients during the early phase of myocardial infarction. A strong correlation between the free thyroxine fraction and free fatty acids suggests that they compete for protein binding sites. The increase in free thyroxine may have undesirable effects on myocardial oxygen demand during acute myocardial infarction.

"Low T3-syndrome" in acute myocardial infarction--relationship to beta-adrenergic blockade and clinical course

Serum levels of T4, T3 rT3 and resin T3 uptake were followed for 5 days in 40 patients with acute myocardial infarction (AMI) allocated to early treatment either with alprenolol or placebo. There was a significant fall in T3 (P less than 0.05) and an increase in rT3 (P less than 0.05) without any significant difference between the alprenolol - (n = 19) and placebo - (n = 21) treated groups. The risk of missing a further 20% change in se-T3 and se-rT3 after alprenolol compared to placebo treatment (beta) was less than 0.10 and less than 0.50, respectively. In patients with a severe clinical course, the fall in T3 and increase in rT3 was significantly greater than in patients without complications. No change in T4 was observed either with respect to the clinical course nor following alprenolol. The data suggest that alprenolol can be given in the acute phase of myocardial infarction without causing any additional disturbance in the serum levels of T3 and T4.

Endogenous cortisol and thyroid hormone levels in patients with acute myocardial infarction

Thyroid hormones and cortisol levels were serially measured over seven mornings and evenings in 23 consecutive patients with acute myocardial infarction (AMI) or acute coronary insufficiency (ACI). The patients were divided into two groups, high level cortisol (HLC) and low level cortisol (LLC) groups, according to mean morning and evening cortisol levels. The transient increase in plasma rT3, decrease in T3 and TSH was significantly greater in the HLC group. A diurnal variation in cortisol levels was observed in the LLC group 48 h and in the HLC group 72 h after admission. Taking the 23 patients together, no significant correlation was observed between infarct size (peak CPK levels) and the altered rT3, T4 or TSH levels. However, a significant correlation was obtained between the maximal change in T3, rT3 or TSH and the mean cortisol levels preceding these alterations, as well as between cortisol levels and infarct size. It is suggested that cortisol rather than infarct size may be the dominant factor involved in the alteration of thyroidal levels in AMI patients.

Thyroid hormones in acute myocardial infarction

Thyroid hormones were serially measured over a 2-week period in thirty-four consecutive patients with acute myocardial infarction (AMI). A transient increase in plasma rT3 and a decrease in plasma T3 was found, with the maximum changes occurring on the third day after the onset of AMI. The changes in plasma rT3 and T3 were greater in the seventeen patients with a complicated AMI (mean peak SGOT 145 mu/l) than in the seventeen patients with an uncomplicated AMI (mean peak SGOT 79 mu/l). A correlation was found between infarct size (as estimated by the peak SGOT value) and the following indices: delta r T3, delta T3, highest rT3/t3 and highest rT3/T4 ratios. A transient increase in plasma TSH (peak on days 4 and 5) and in plasma T4 and FT4 index (peak on days 6 and 7) was also observed, whereas T3 resin uptake (T3U) decreased. These findings suggest that the following sequence of events occurs in thyroid hormone metabolism during AMI: (1) inhibition of the 5'-deiodination of T4, resulting in increased plasma rT3 and decreased plasma T3 values, and in a lower metabolic clearance of T4. (2) Increased secretion of TSH (provoked by the lower T3 levels) resulting in increased thyroidal secretion of T4 and T3, which is then switched off by the negative feedback of thyroid hormones on the pituitary.

Thyroid function after thermal trauma

The thyroid function was analyzed for 4-6 weeks in a prospective study of 12 thermally injured patients. The burn size range was 15-90%. Serum concentrations of 3,5,3'-triidothyronine (T3) was suppressed and 3,3',5'-triidothyronine (rT3) was increased. The ratio T3/rT3 was subnormal on the third day after the trauma and normalized after 3 weeks. Thyroxine and the free T4-index were within the normal range. The free T3-index were within the normal range. The TSH concentration was initially low but slowly increasing during the period of study. The concentration of the thyroxine-binding globulin (TBG) varied within the normal range. The T3 resin uptake test varied inversely with the TBG concentration. The concentration of thyroxine-binding prealbumin (TBPA) was subnormal. A control experiment excluded possible interference on the hormone concentrations of administered donor blood and plasma. It is concluded that the thyroid hormones are not responsible for the posttraumatic hypermetabolism in burn injury. The present findings further indicate a depletion of metabolically active thyroid hormones at the cellular level after burn injury.