Letter: Thyroid-hormone levels and prognosis in patients with serious non-thyroidal illness

A prognostic role for non-thyroidal illness syndrome in chronic renal failure:a systematic review and meta-analysis

BACKGROUND

Chronic renal failure (CRF) is a serious disease that has become a burden on global and local economics and public health. In addition, non-thyroidal illness syndrome (NTIS) has become increasingly more prevalent in CRF patients.

MATERIALS AND METHODS

A data search was conducted on the PubMed/Medline, Cochrane Library, Web of Science, Embase, and CBM databases to identify studies up to November 1st, 2018, that compared low T3 and normal T3 levels in patients with CRF. Data analysis was done by calculating the relative risks (RR) and 95% confidence intervals (95% CI) and continuous variables were described by weighted mean difference (WMD) and 95% CI. The efficacy outcomes included renal function and mortality. The Newcastle-Ottawa Scale and Agency for Healthcare Research and Quality scale were used to assess the quality of the cohort and cross-sectional studies, respectively. A funnel plot was used to identify publication bias.

RESULTS

Seventeen studies with a total of 4593 patients were finally included in the analysis. Among the 17 studies, 11 reported the mortality of CRF patients with low T3 and normal T3 levels. Subgroups were assigned according to different follow-up times and different methods of treatment. The mortality rate in the low T3 group was much higher than in the normal T3 group. 11 studies reported creatinine (Cr) results in patients with low T3 and normal T3 levels and our analysis found no significant differences between the two groups (95%CI: 0.46-0.25; P-heterogeneity = 0.000; P = 0.559). Five studies reported uric acid results and we found no significant differences between the two groups (95%CI: 0.08-0.22; P-heterogeneity = 0.438; P = 0.377). Five studies reported the urea levels in the two groups and our analysis found no significant differences (95%CI: 1.60-1.23; I² = 0.0%; P-heterogeneity = 0.498;P = 0.798).

CONCLUSION

Low T3 had a greater impact on the short-term prognosis of patients with CRF than on the long-term prognosis. NTIS did not cause substantial kidney damage.

Non-thyroidal illness syndrome in patients with cardiovascular diseases: A systematic review and meta-analysis

BACKGROUND

Non-thyroidal illness syndrome (NTIS) is characterized by decreased serum triiodothyronine level without increased thyroid-stimulating hormone level during critical illness. The summary data on the prevalence of NTIS in cardiovascular patients are lacking, and its prognostic role in cardiovascular patients is also unclear.

METHODS

We performed a systematic review and meta-analysis to comprehensively determine the prevalence and the prognostic role of NTIS in cardiovascular patients. The prevalence of NTIS was pooled using random-effect meta-analysis and the hazard ratios (HRs) for all-cause mortality, cardiac mortality and major adverse cardiovascular events (MACE) were also pooled.

RESULTS

Forty-one studies were finally included. The pooled prevalence of NTIS in cardiovascular patients was 21.7% (95% CI 18.4%-25.3%). Subgroup by the types of cardiovascular diseases showed the prevalence of NTIS was highest in patients with heart failure (24.5%), followed by acute myocardial infarction (18.9%) and acute coronary syndrome (17.1%). Meta-analysis of studies using strict diagnostic criteria of NITS showed that the pooled prevalence of NTIS in cardiovascular patients was 17.6% (95% CI 14.5%-21.2%). NTIS was independently associated with increased risks of all-cause mortality (HR=2.52, 95% CI 1.87-3.40, P<0.001) and cardiac mortality (HR=2.06, 95% CI 1.58-2.69, P<0.001) in cardiovascular patients. NTIS was also an independent predictor of MACE in cardiovascular patients (HR=1.73, 95% CI 1.32-2.26, P<0.001).

CONCLUSION

NTIS is very common in patients with cardiovascular diseases. NTIS is an independent prognostic factor in cardiovascular patients and is associated with increased risks of all-cause mortality, cardiac mortality and MACE.

Free thyroxine level as an independent predictor of infection-related mortality in patients on peritoneal dialysis: a prospective multicenter cohort study

BACKGROUND

Previous studies have reported the relationship between thyroid hormone levels and mortality in dialysis patients. However, little is known about the association of free thyroxine (fT4) and mortality in patients on peritoneal dialysis (PD). This study investigated the association between basal and annual variation in fT4 level and mortality in PD patients.

METHODS

Patients on maintenance PD were enrolled from a prospective multicenter cohort study in Korea; their serum triiodothyronine, fT4, and thyroid-stimulating hormone levels were measured 12 months apart. Patients with overt thyroid disease and those receiving thyroid hormone replacement therapy were excluded from the analysis. Patients were divided into two groups based on the median levels of fT4. The differences of all-cause, infection-related, and cardiovascular mortalities were analyzed between the two groups. The association of basal levels and annual variation with mortality was investigated with Kaplan-Meier curves and Cox proportional hazard models.

RESULTS

Among 235 PD patients, 31 (13.2%) deaths occurred during the mean follow-up period of 24 months. Infection (38.7%) was the most common cause of death. Lower basal fT4 levels were an independent predictor of all-cause and infection-related death (hazard ratio [HR] = 2.74, 95% confidence interval [CI] 1.27-5.90, P = 0.01, and HR = 6.33, 95% CI 1.16-34.64, P = 0.03, respectively). Longitudinally, patients with persistently lower fT4 levels during the 12-month period had significantly higher all-cause mortality than those with persistently higher levels (HR = 3.30, 95% CI 1.15-9.41, P = 0.03). The area under the receiver operating characteristic curve of fT4 for predicting all-cause and infection-related mortality was 0.60 and 0.68, respectively.

CONCLUSIONS

fT4 level is an independent predictor of mortality and is especially attributable to infection in PD patients. This predictor was consistent when considering both baseline measurements and annual variation patterns. Close attention to infection in PD patients with relatively lower fT4 levels should be considered.

Baseline levels and trimestral variation of triiodothyronine and thyroxine and their association with mortality in maintenance hemodialysis patients

BACKGROUND AND OBJECTIVES

Conflicting evidence exists with regard to the association of thyroid hormones and mortality in dialysis patients. This study assesses the association between basal and trimestral variation of thyroid stimulating hormone, triiodothyronine, and thyroxine and mortality.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In 210 prevalent hemodialysis patients, serum triiodothyronine, thyroxine, thyroid stimulating hormone, and interleukin-6 were measured 3 months apart. Cardiovascular and non-cardiovascular deaths were registered during follow-up. Based on fluctuations along tertiles of distribution, four trimestral patterns were defined for each thyroid hormone: persistently low, decrease, increase, and persistently high. The association of baseline levels and trimestral variation with mortality was investigated with Kaplan-Meier curves and Cox proportional hazard models.

RESULTS

During follow-up, 103 deaths occurred. Thyroid stimulating hormone levels did not associate with mortality. Patients with relatively low basal triiodothyronine concentrations had higher hazards of dying than patients with high levels. Longitudinally, patients with persistently low levels of triiodothyronine during the 3-month period had higher mortality hazards than those having persistently high levels. These associations were mainly attributable to cardiovascular-related mortality. The association between thyroxine and mortality was not altered after adjustment for triiodothyronine.

CONCLUSIONS

Hemodialysis patients with reduced triiodothyronine or thyroxine levels bear an increased mortality risk, especially due to cardiovascular causes. This was true when considering both baseline measurements and trimestral variation patterns. Our longitudinal design adds observational evidence supporting the hypothesis that the link may underlie a causal effect.

Serum thyroid hormones levels are significantly decreased in septic neonates with poor outcome

The aim of this prospective study was to investigate the effects of thyroid hormone levels on the sepsis criteria and mortality in septic newborns. This study was performed at the Firat University Hospital Neonatal Intensive Care Unit. A group of septic newborns and a control group of healthy non-infected newborns were evaluated. Blood samples were obtained at onset from septic and healthy newborns and at 10th day of the antibiotic therapy from only septic newborns, and thereafter serum total T(3) (TT(3)), total T(4) (TT(4)), and TSH levels were determined. A total of 292 newborns were included in the study. Serum TT(3) levels at onset and at 10th day of the antibiotic therapy were 163.8±63.4 and 178.3±33.1 ng/dl, TT(4) levels were 6.9±2.2 and 11.0±2.6 mg/ml, and TSH levels were 3.8±2.1 and 4.0±2.5 μU/ml, respectively in septic newborns. Serum TT3 levels were 180.3±47.6 ng/dl, TT(4) levels were 10.9±2.3 mg/ml, and TSH levels were 4.1±2.2 μU/ml in healthy newborns. Serum TT(3), TT(4) levels of septic newborns were significantly decreased with respect to those of healthy newborns at onset and serum TT(4) levels was increased significantly after antibiotic therapy. To the best of our knowledge, this report is the first study to compare thyroid hormone levels in a large number of septic newborns and a healthy group. Our findings suggest that before and after treatment of neonatal sepsis a significant change is realized in thyroid hormone levels.

The effect of body temperature on thyroid hormone levels in patients with non-thyroidal illness

During studies on the mechanism underlying the low serum T3 levels in euthyroid patients with various acute and chronic non-thyroidal illnesses, it became evident that body temperature may be one parameter associated with changes in serum T3 levels. Forty-nine hospitalized, euthyroid patients with hyperpyrexia caused by various non-thyroidal illnesses were studied. The levels of serum T3 were found to decrease gradually with increasing body temperature. T3 was already below the normal level +/- 2 S.D. at a body temperature of around 38 degrees C. Such low T3 levels as were seen at temperatures of above 40 degrees C are observed in thyroid patients only during severe hypothyroidism. The levels of T4 and TSH remained unchanged and within the normal range regardless of body temperature. The levels of reverse-T3 in the sera analyzed were found to be unchanged in some cases, while in others they paralleled body temperature. It is concluded that the body temperature must be taken into consideration when studying the serum levels of T3.

Serum cortisol and thyroid hormone levels in neonates with sepsis

OBJECTIVE

To evaluate the thyroid hormone and cortisol levels in neonates with sepsis in relation to the final outcome. It was hypothesized that the hormonal level could act as some prognostic guideline.

METHODS

Forty nine neonates, aged 8- 28 days, diagnosed as neonatal sepsis were selected for the study. Neonates below 8 days of age, 35 weeks of gestation and 2000 g of birth weight were excluded from the study. Twenty FT-AGA neonates beyond day 7 of life served as control for the study. The hormones were estimated by radioimmunoassay.

RESULTS

The neonates with sepsis had significantly higher mean serum cortisol and lower mean serum total T4 at admission as compared to healthy neonates. The mean serum total T3 level was also lower, but the difference was not statistically significant. The mean serum TSH levels were comparable in both groups. The levels normalised following recovery. Sixteen neonates succumbed to the disease process. The non-survivors had significantly lower mean total T3 and total T4 levels as compared to the survivors.

CONCLUSION

The endocrinal abnormalities are of transient nature as a response to sepsis. Low total T3 and total T4 are the predictors of adverse outcome in neonates with sepsis.

Nutritional and prognostic significance of serum hypothyroxinemia in hospitalized patients with liver cirrhosis

BACKGROUND/AIMS

A variety of severe illnesses can induce changes in thyroid hormone metabolism, leading to findings referred to as "sick euthyroid syndrome". In several groups of patients the reduction of serum thyroxine concentration (T4), characteristic of the low-T4 variant of sick euthyroid syndrome, has been found to be a good predictor of survival. Although the pathophysiology of hormonal alterations has not yet been defined, nutritional deficits have been suggested to play a role. The study aimed to define the prognostic and nutritional significance of serum thyroxine in liver cirrhosis.

METHODS

Thyroid hormones and nutritional status were evaluated in a group of 75 consecutive hospitalized patients with cirrhosis, followed-up clinically for 12 months.

RESULTS

A low-T4 variant of sick euthyroid syndrome was found in 23 of the 75 enrolled patients with cirrhosis (30.6%). Serum T4, but not serum T3, correlated with mid-arm muscle circumference (p < 0.01), an indicator of muscle protein compartment. While both serum T3 and T4 correlated directly with serum proteins and inversely with Child-Pugh score, only T4 was predictive of outcome. Patients with the low-T4 variant of sick euthyroid syndrome showed significantly lower short- and long-term survival rates compared to those with normal serum T4 concentrations (p < 0.008 at 3 months, p < 0.001 at 6 months and 1 year). A multivariate analysis using the proportional hazards Cox's regression procedure showed that serum T4, but not serum T3 or nutritional parameters, improves the prognostic capacity of Child-Pugh score (p < 0.01).

CONCLUSIONS

These data indicate that the low T4-variant of sick euthyroid syndrome distinguishes a subgroup of patients with cirrhosis at risk for decreased survival. The inclusion of T4 in the Child-Pugh score, by improving its prognostic power, may optimize the selection of patients with advanced cirrhosis to receive specific therapy such as transplantation.

Relations between the selenium status and the low T3 syndrome after major trauma

OBJECTIVE

Thyroxine (T4) is deiodinated to triiodothyronine (T3) by the hepatic type I iodothyronine deiodinase, a selenoprotein that is sensitive to selenium (Se) deficiency. After severe injury, T4 deiodination is decreased, leading to the low T3 syndrome. Injury increases free radical production, which inactivates the iodothyronine deiodinase. The aims were to study the Se status after major trauma and to investigate its relation to the low T3 syndrome.

DESIGN

Preliminary prospective descriptive study.

SETTING

Intensive care unit at a university teaching hospital.

PATIENTS AND METHODS

11 patients aged 41 +/- 4 years (mean +/- SEM), with severe multiple injuries (Injury Severity Score 29 +/- 2 points). A balance study was performed from day 1 to day 7. Serum and urine samples were collected from the time of admission until day 7, then on days 10, 15, 20, 25 and 30. Non-parametric tests and Pearson's correlation coefficients were used for analysis.

RESULTS

Cumulated Se losses were 0.88 +/- 0.1 mumol/24h. Serum Se was decreased from admission to day 7. T3, free T3, and the T3/T4 ratio were low until day 5, being lowest on day 2; T4 and thyroid stimulating hormone were normal. Serum Se was correlated with T3 (r = 0.55, p = 0.0001), and with free T3 (r = 0.35).

CONCLUSION

Se status is altered after trauma, with decreased Se serum levels upon admission to the ICU but with no major Se losses. Se is probably redistributed to the tissues. The correlation between Se and T3, along with the parallel decrease in T4 deiodination, indicates that reduced deiodination might be related to the transient decrease in serum Se.

Relationship of admission thyroid function tests to outcome in critical illness

One hundred and eighty patients had serum thyrotropin, total triiodothyronine and free thyroxine concentrations measured within 3 h of admission to the Intensive Therapy Unit to assess whether thyroid function tests could predict outcome in critical illness. Overall mortality was 30.6%. Nonsurvivors were older (p = 0.001), and had higher APACHE II scores (p < 0.001) and predicted mortalities (p < 0.001). There was no difference in the median values of thyrotropin, total triiodothyronine and free thyroxine concentrations between survivors and nonsurvivors. Thyrotropin concentration was subnormal in 15 patients, normal in 152 and elevated in 13 patients. In contrast, 80 patients had subnormal triiodothyronine concentration. Free thyroxine was subnormal in five patients. Thyrotropin, total triiodothyronine and free thyroxine concentrations were not related to outcome (p = 0.360, p = 0.622, p = 0.726, respectively). No variable independently predicted death. Total triiodothyronine concentrations were lower in patients who received dopamine before admission to the intensive therapy unit than those who did not (p = 0.008); thyrotropin and free thyroxine concentrations were not influenced by dopamine administration. Serum concentrations of thyrotropin, total triiodothyronine and free thyroxine measured within 3 h of admission to the intensive therapy unit are not predictive of outcome.

Effect of triiodothyronine on postischemic myocardial function in the isolated heart

Thyroid dysfunction has been shown to have a significant impact on hemodynamic status and cardiac function. The purpose of this study was to determine the influence of triiodothyronine (T3) on cardiac functional recovery after ischemia in a dose-dependent manner. Postischemic functional recovery was assessed in isolated rabbit hearts mounted in a modified Langendorff preparation. Left ventricular systolic, diastolic, and peak developed pressures were measured before and after ischemia, and calculated as a percentage of preischemic function. Two cohorts of hearts were studied: the first was exposed to warm ischemia until a myocardial contracture of 4 mmHg was produced; the second cohort was exposed to warm ischemia until a contracture of 15 mm Hg was observed. In each cohort, T3 was added to the perfusion solution after ischemia in a physiologic concentration (2.5 x 10(-9) g/mL; 1 x T3), as well as ten times (2.5 x 10(-8) g/mL; 10 x T3) and a hundred times (2.5 x 10(-7) g/mL; 100 x T3) the physiologic concentration. One group, given the carrier only but without T3, served as the control. Rabbit hearts exposed to a short period of ischemia (4-mmHg diastolic contracture) showed increased recovery with 1 x T3 and 10 x T3. 100 x T3 did not bring about improved left ventricular recovery versus that in the control group. Rabbit hearts in the 15 mm Hg-diastolic contracture cohort showed increased recovery with 10 x T3 but not with 1 x T3. 100 x T3 led to decreased recovery in this cohort versus that in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Thyrotropin concentration predicts outcome in critical illness

Concentrations of thyrotropin, total thyroxine, total tri-iodothyronine and cortisol were measured on admission to an intensive care unit in 200 consecutive patients who did not receive dopamine. Thyrotropin concentration was subnormal (< 0.4 mU.l-1) in 25 patients (12%) and increased (> 5.0 mU.l-1) in 27 (13%). Mortality in these groups differed 22-fold (88% and 4% respectively) despite comparable APACHE II outcome predictions (51% and 32%). Thyrotropin concentration correlated positively with total thyroxine concentration (r = 0.46, p < 0.001) and negatively with cortisol concentration (r = -0.56, p < 0.001). In 15 of the patients with increased thyrotropin concentration on admission, repeat measurements were made on recovery and were normal in 13. The high frequency of abnormal thyrotropin concentrations casts doubt on the assumption of euthyroidism in critical illness. Admission thyrotropin concentration is of prognostic value in critically ill patients.

The effects of infusion of amino acids alone or in combination with glucose and fat on thyroid hormone and other metabolite interactions in surgery

The effects of infusion of amino acids alone or in combination with carbohydrate and lipid on triiodothyronine (T3) and reverse triiodothyronine (rT3) status, substrate availability and metabolism in surgically-stressed and clinically euthyroid patients were examined. The characteristic post-operative decline in T3 concentration was observed in all patient groups (p < 0.001) (8 patients in each group). However, infusion with amino acids alone retarded the decline in T3; the decrease was lower than those found in the controls and the mixed nutrition group and restoration of T3 values was incomplete, even by the sixth post-operative day. The pattern of increase in rT3 was similar in all 3 patient groups. However, the T3/rT3 ratio dropped to its lowest level on day 1 in the control group and the mixed infusion group (p < 0.001), with a complete restoration by the sixth post-operative day, whereas in the amino acids infused group the ratio was lowest on day 2 (p < 0.001) and was still significantly low by day 6 compared with the pre-operative value (p < 0.001). The findings, in the group infused with amino acids of a less prominent hyperglycaemia, with the significant slowing of T3 response and the significant correlation of rT3 with the plasma glucose, indicate a link between hyperglycaemia and the thyroid hormone response to surgical trauma. No correlations were found between thyroid hormone or urea concentrations, and the blood concentrations of free fatty acids, 3-hydroxybutyrate, or urea; or between thyroid hormone and the percentage of total urea nitrogen excretion. Results show that the changes in fat metabolism after operation are unlikely to be responsible for the changes in T3 and rT3. In conclusion, whereas the post-operative response of T3 concentration can be partially modified by the nutrition regimen employed, that of rT3 is largely related to surgical stress.

Do thyroid function tests independently predict survival in the critically ill?

We studied the ability of thyroid function tests to predict hospital survival in 116 critically ill patients and compared the results with independent predictions of survival made by critical care physicians. Eleven patients (9.5%) had clinically unsuspected hypothyroidism and were less likely to survive (p = 0.03). In patients critically ill with nonthyroidal disease, low T3, low FT3I, low T4, low FT4I, high TSH, and high T3U levels each showed significant correlation with nonsurvival (all p less than 0.02). Of these, however, only low T3 (p less than 0.001) and high TSH (p = 0.016) showed significant independent prediction of nonsurvival, and only low T3 (p = 0.011) added any significant independent prediction of nonsurvival beyond that made clinically by the group of critical care physicians.

Triiodothyronine in the recovery of stunned myocardium in dogs

Two groups of dogs were subjected to a 15-minute period of regional myocardial ischemia by snaring the left anterior descending coronary artery proximal to its first diagonal branch. After release of the snare, the dogs were given either placebo (group 1: n = 7) or triiodothyronine (T3) therapy (group 2: n = 6). The dose of T3 given was 0.2 microgram/kg at 30-minute intervals to a total of six doses. Plasma free T3 level fell significantly during the ischemic period in both groups and continued to fall after reperfusion in group 1. In both groups, cardiac function deteriorated significantly during the period of ischemia and rapidly returned to control level after reperfusion. After 90 minutes of reperfusion, however, deterioration of left ventricular function was observed in group 1 and was significantly worse than in group 2, in which hemodynamic function was maintained and, in fact, improved to levels superior to control. It is suggested that T3 therapy may be worthy of trial in patients in whom reperfusion of the myocardium takes place after a relatively short ischemic period (the "stunned myocardium").

Hormonal changes in cerebral infarction in the young and elderly

Fifty-one patients with CCT verified cerebral infarction were submitted to serum and CSF radioimmunoassay of FSH, LH, estradiol (E2), progesterone, testosterone, cortisol and T4. The results were compared to those of 82 matched controls. Our findings suggest that (1) high serum E2 is a risk factor of stroke in males; (2) low serum T4 is a risk factor in males; (3) serum testosterone is reduced in acute stroke in males confirming that it is stress sensitive; (4) serum LH was higher in hypertensive thrombotic males when compared to normotensive ones, and (5) FSH, LH, E2 and T4 are undetectable in CSF of patients and controls.

Is oleic acid the thyroxine binding inhibitor in the serum of ill patients?

The possibility that oleic acid is the thyroxine binding inhibitor in the serum of seriously ill patients was investigated. 3H-Oleic acid was shown to bind directly to human thyroxine-binding globulin (TBG) by the techniques of one and two-dimensional immunoelectrophoresis in combination with autoradiography. However, no correlation was seen between serum thyroxine concentration and oleic acid concentration in two groups of patients, one of which underwent routine cholecystectomy, whilst the other group was admitted to an intensive therapy unit (mortality 75%). No correlation was seen between serum total thyroxine concentration and either stearic, palmitic, linoleic or arachidonic acid concentrations in these groups. Therefore, it was concluded that oleic acid was unlikely to be the circulating inhibitor of thyroxine binding.

Triiodothyronine increases survival in canine hemorrhagic shock

The euthyroid sick (low T3) syndrome occurs in shock and could influence survival. To evaluate the potential therapeutic value of triiodothyronine (T3) in circulatory collapse, 26 anesthetized, heparinized mongrel dogs were bled rapidly into a reservoir until mean arterial blood pressure (MAP) = 40 mmHg. After 60 min of hypotension, the animals were given 15 micrograms/kg of T3 i.v. (13 dogs) or an equal volume of normal saline (13 dogs), and the reservoir line was clamped for 30 min (uncompensated shock). The shed blood was then reinfused over 30 min. After 1 h of monitoring the dogs were returned to the kennel and observed for 3 days. T3 (15 micrograms/kg) or normal saline was administered i.v. on each of the first 3 postshock days. T3 administration caused significant increases during uncompensated shock in cardiac output, stroke volume, mean arterial pressure, right and left ventricular stroke work and systemic vascular resistance, with a decrease in pulmonary vascular resistance. Shortly after reinfusion of shed blood, hemodynamic values were similar in T3 and untreated animals. In the control group, 6 of 13 dogs died. However, only one of 13 T3 dogs died (P less than 0.05). Although the mechanism by which T3 enhances shock survival was not clearly identified, T3 might exert beneficial effects via the hypothalamic-pituitary-thyroid axis or by acting on cardiovascular receptors to improve hemodynamic function at a critical stage of shock. Additional studies of T3 therapy in clinical shock appear warranted.

A longitudinal evaluation of thyroid function in critically ill surgical patients

Thyroid hormone alterations (known as the "sick-euthyroid syndrome") are common following major surgery, but the time course for appearance and recovery from these alterations has not previously been longitudinally studied in a large group of surgical patients. The authors prospectively studied 59 patients undergoing major surgery (coronary artery bypass grafting, pneumonectomy, or subtotal colectomy). Compared with preoperative values, the mean serum T4, T3, free T3, and TSH concentrations decreased significantly (p less than 0.05) following surgery. Serum reverse T3 and T3 resin uptake index increased, while free T4 levels remained unchanged. These changes were seen within 6 hours of surgery and normalized by 1 week after surgery. Although the serum TSH response to TRH was normal before and after surgery in 56 of the 59 patients, the maximal TRH-induced increase in serum TSH and the integrated serum TSH response to TRH were suppressed in the early perioperative period. This postoperative TSH suppression correlated with elevated postoperative plasma dopamine concentrations (r = 0.57, p less than 0.05). Three patients with compensated primary hypothyroidism were detected in the study and represent the first documentation of serial thyroid hormone and TSH levels in hypothyroid patients undergoing major surgery. These patients had similar changes in thyroid hormone values compared with euthyroid patients. The serum TSH response to TRH was suppressed into the normal range in two of these patients on the day following surgery. The authors conclude that the sick-euthyroid syndrome occurs within a few hours of major surgery and remits with convalescence. Postoperative decreases in serum TSH may mask the diagnosis of hypothyroidism. Surgical consultants should be aware of these rapid postoperative changes so that thyroid function tests are properly interpreted in patients who have undergone major surgery.

Effects of open-heart surgery on thyroid hormone levels

The effect of heart surgery with and without cardiopulmonary by-pass on plasma levels of thyroxine (T4) and triiodothyronine (T3) was studied in 19 patients. It was found that even before the operation the plasma levels of T4 and of T3 were significantly lower in the by-pass group of patients in comparison with those without by-pass. This lower level of thyroid hormones could be explained by greater pre-operative stress. This presumption is supported by the finding of the greater pre-operative plasma concentrations of dopamine-beta-hydroxylase and growth hormone in patients of the by-pass group. While in patients not undergoing CPB a tendency to the decrease of plasma thyroid hormones was observed during the early postoperative phase, in patients of the by-pass group a small increase was observed. On the basis of the finding that thyroid hormones exercise powerful and specific effect on myocardial contractility, it is suggested that the low hormone level might have a role in the pathogenesis of postoperative low cardiac output syndrome.

Beneficial effect of practolol in preventing adrenaline-induced systemic and myocardial metabolic changes

The aim of the study was to investigate whether the beta blocking agent, practolol, is able to modify some of the metabolic and hormonal responses and the local myocardial changes evoked by an excess of adrenaline similar to that seen after acute coronary occlusion. Adrenaline (1.2 micrograms/kg/min) and practolol (1 mg/kg) were infused concurrently to anaesthetized intact dogs for 5 h. Blood free fatty acid and triiodothyronine levels were measured initially and after 2, 4 and 5 h of infusion. At the end of the infusion the myocardium was subjected to biochemical, histoenzymatic and electron microscopic examination. The results were compared with those obtained in dogs infused with adrenaline alone and with saline alone. Practolol reduced the adrenaline-induced increase in free fatty acids and a fall in triiodothyronine in the blood. Myocardial acetate accumulation and ATP decrease were both reduced by practolol. Histoenzymatic and electron microscopic changes were less. These effects of practolol upon systemic and myocardial disturbances induced by the excess of adrenaline indicate that it might be effective in modifying any excessive adrenergic response which may occur in acute myocardial infarction.

Thyroxine, triiodothyronine and thyrotrophin levels in meningococcal meningitis, typhoid fever and other febrile conditions

Thyroid status was estimated serially by measuring triiodothyronine (T3), thyroxine (T4) and thyrotrophin (hTSH) in 20 patients suffering from meningococcal meningitis, typhoid fever and other acute febrile illnesses. Significantly low T3 and only slightly increased T4 were observed in all the patients. hTSH was normal in all of these. A significant reciprocal relationship was found between the degree of fever and fall in T3 concentrations. T3 tended to rise in patients who recovered but in those who deteriorated or died, T3 remained persistently low.

Lowering of serum 3,3',5-triiodothyronine thyroxine ratio in patients with myocardial infarction; relationship with extent of tissue injury

Serial measurements of haematocrit (Ht), plasma thyroxine (T4), triiodothyronine (T3) and alpha-hydroxybutyrate dehydroxygenase (alpha-HBDH) were performed in patients following myocardial infarction (MI). Infarct size was estimated by mathematical analysis of the change in plasma alpha-HBDH activity with time. After an initial small increase Ht decreased 12% until day 9 and remained constant thereafter. Serum T4 did not change during the entire study. Serum T3 decreased to 66% at day 9 and then returned to normal within 2 months. These figures are expressed relative to determinations in the first blood sample obtained within 12 h after MI. A significant correlation between the lowest serum T3/T4 ratio and infarct size was observed. These observations suggest that in these patients the peripheral conversion of T4 into T3 is reduced. This was accompanied by an increased production of reverse T3 as evidenced by observations in one patient.

Changes in the circulating thyroid hormones during anaesthesia and thyroid surgery

The circulating thyroid hormones were found to respond to general anaesthesia and surgery of the thyroid gland in a similar manner to that reported with general surgery. When compared with the preoperative plasma concentration, the post-operative thyroxine levels showed a significant rise, whereas the triiodothyronine level fell.

Diagnosis of hyperthyroidism when serum-thyroxine alone is raised

31 patients admitted to hospital with different non-thyroidal intercurrent diseases were found to have raised total serum-thyroxine (T4) and free T4 together with normal serum-triiodothyronine (T3) concentrations. At admission none was clinically hyperthyroid. Patients were assigned to 3 groups according to clinical course and the laboratory findings. In the first group (14 patients) classic hyperthyroidism developed after recovery from the intercurrent disease. 11 out of these 14 patients had recently received iodine-containing preparations. In a second group (11 patients) the initially raised serum-T4 rapidly returned to normal with recovery from the non-thyroidal disease. In a third group (6 patients) serum-T4 concentrations remained raised well after recovery from intercurrent disease. In this group, there were 2 cases of transient iodine-induced (Jod-Basedow) hyperthyroidism in which raised serum-T4 returned spontaneously to normal after several months as iodine was eliminated. These results indicate that increase in serum-T4 with normal serum-T3 in patients with intercurrent systemic disease is not always the result of hyperthyroidism and in many cases probably reflects changes in peripheral metabolism of T4. It is suggested that careful clinical follow-up is needed in patients with raised serum-T4 and normal serum-T3 for the early detection and treatment of classic hyperthyroidism.

Reduced active thyroid hormone levels in acute illness

In acute and subacute disease the active thyroid hormones, triiodothyronine (T3) and tetraiodothyroacetic acid (tetrac), are decreased while serum-thyroxine (T4) levels tend to be slightly reduced. Conversely, the inactive metabolite, reverse triiodothyronine (reverse T3), is increased indicating a diversion of T4 metabolism from an activating to an inactivating pathway. With convalescence the serum levels of T3, tetrac, and T4 recover while reverse T3 decreases to normal. These changes occur without significant alterations in serum levels of thyroid-stimulating hormone, indicating maintenance of euthyroidism throughout disease.

Serum triiodothyronine and reverse triiodothyronine concentrations after surgical operation

Serum-triiodothyronine (T3) concentrations fell rapidly after surgery in six out of seven initially euthyroid patients. Simultaneous increases in reverse triiodothyronine (rT3) concentrations suggested that the peripheral monodeiodination of thyroxine (T4) proceeds by an alternative pathway in the postoperative period.