Evaluation of pituitary-thyroid axis response to acute myocardial infarction

Management of Hypothyroidism in Patients with Acute Myocardial Infarction

Background and Objectives: Thyroid hormones (TH) affect cardiac function through effects on cardiac contractility and systemic vascular resistance. While TH replacement for patients with hypothyroidism might be necessary for restoration of cardiac output after an acute myocardial infarction (AMI), it could theoretically lead to excessively rapid restoration of the metabolic rate. The appropriate management of hypothyroidism in patients with AMI is unknown. We describe the practice patterns in the management of hypothyroidism in the setting of AMI as well as patients’ clinical outcomes. Material and Methods: Retrospective study of patients that were admitted to a tertiary care hospital with AMI and newly diagnosed or uncontrolled hypothyroidism (TSH ≥ 10 mIU/L) between 2011–2018. Eligible patients were identified using diagnosis codes for AMI and laboratory values, followed by medical record review. We categorized patients according to treatment status with TH and by degree of hypothyroidism. Clinical outcomes included: 30-day mortality/readmission, bleeding, stroke, arrhythmia, sudden cardiac death, and new or worsening heart failure. Summary statistics and group comparisons are presented. Results: Sixty-four patients were included, their median age was 64 years and 61% (n = 39) were women. Most of the patients (59%) had a documented history of hypothyroidism. Of these, all were restarted on levothyroxine (LT4) during the index admission when compared to patients without a history of hypothyroidism, of which 54% received LT4 treatment (p = 0.001). The median TSH in those treated with LT4 was higher (25 mIU/L) when compared to those who were not (12 mIU/L), (p = 0.007). Patients who received intravenous LT4 had higher TSH levels and other variables suggesting worse clinical presentation, but these differences were not statistically significant. No statistically significant differences were noted on clinical outcomes according to LT4 treatment status. Conclusion: A history of hypothyroidism and the degree of TSH elevation seem to guide the management of hypothyroidism in patients with AMI. The clinical effect of correcting hypothyroidism in this setting requires further evaluation.

Triiodothyronine replacement in critically ill adults with non-thyroidal illness syndrome

PURPOSE

Non-thyroidal illness syndrome is commonly encountered in critically ill patients, many of whom are treated with thyroid hormones despite uncertainty regarding their safety and effectiveness. This retrospective observational study sought to evaluate the utilization, safety, and effectiveness of triiodothyronine (T3) supplementation in critically ill adults admitted to either of two non-cardiac surgery mixed-medical/surgical intensive care units (ICU).

METHODS

Consecutive adults admitted to an ICU and treated with enterally administered T3 were identified over a two-year period. Data pertaining to demographics, T3 utilization, safety, and clinical outcomes were collected.

RESULTS

Data were extracted from the medical records of 70 consecutive patients. All had baseline serum free T3 concentrations below the lower limit of our laboratory's reference range and 22 (31%) patients also had low thyroxine (T4) concentrations. The most commonly prescribed replacement doses were 25 and 50 µg for a median of seven days and almost half of the patients also received concomitant T4 supplementation. Serum thyroid hormones were available in 48 of 70 patients (69%) at a median [interquartile range (IQR)] of 7 [6-38] days. Normalization of free T3 serum concentrations occurred in 30 of 48 patients (63%) at a median [IQR] of 8 [7-33] days. A dose-response relationship was identifiable. New adverse events (atrial fibrillation/flutter, hypertension, sinus tachycardia, myocardial infarction) during therapy were less frequent than at baseline.

CONCLUSIONS

This study suggests that with T3 supplementation there was evidence of serum free T3 normalization without evidence of associated harms. A definitive trial is needed to evaluate clinical effectiveness.

Thyroid-stimulating hormone and adverse left ventricular remodeling following ST-segment elevation myocardial infarction

BACKGROUND

Adverse left ventricular remodeling is one of the major determinants of heart failure and mortality in patients surviving ST-segment elevation myocardial infarction (STEMI). The hypothalamic-pituitary-thyroid axis is a key cardiovascular regulator; however, the relationship between hypothalamic-pituitary-thyroid status and post-STEMI left ventricular remodeling is unclear. We aimed to investigate the association between thyroid-stimulating hormone concentrations and the development of left ventricular remodeling following reperfused STEMI.

METHODS

In this prospective observational study of 102 consecutive STEMI patients, thyroid-stimulating hormone levels were measured at the first day after infarction and 4 months thereafter. Cardiac magnetic resonance scans were performed within the first week as well as at 4 months follow-up to determine infarct characteristics, myocardial function and as primary endpoint left ventricular remodeling, defined as a 20% or greater increase in left ventricular end-diastolic volume.

RESULTS

Patients with left ventricular remodeling (n=15, 15%) showed significantly lower concentrations of baseline (1.20 [0.92-1.91] vs. 1.73 [1.30-2.60] mU/l; P=0.02) and follow-up (1.11 [0.86-1.28] vs. 1.51 [1.15-2.02] mU/l; P=0.002) thyroid-stimulating hormone. The association between baseline thyroid-stimulating hormone and left ventricular remodeling remained significant after adjustment for major clinical (peak high-sensitivity cardiac troponin T and C-reactive protein, heart rate; odds ratio (OR) 5.33, 95% confidence interval (CI) 1.52-18.63; P=0.01) and cardiac magnetic resonance predictors of left ventricular remodeling (infarct size, microvascular obstruction, ejection fraction; OR 4.59, 95% CI 1.36-15.55; P=0.01). Furthermore, chronic thyroid-stimulating hormone was related to left ventricular remodeling independently of chronic left ventricular remodeling correlates (infarct size, ejection fraction, left ventricular end-diastolic volume, left ventricular end-systolic volume; OR 9.22, 95% CI 1.69-50.22; P=0.01).

CONCLUSIONS

Baseline and chronic thyroid-stimulating hormone concentrations following STEMI were independently associated with left ventricular remodeling, proposing a novel pathophysiological axis in the development of post-STEMI left ventricular remodeling.

The Prognostic Value of Severe Malnutrition in the Development of Nonthyroidal Illness in Head and Neck Cancer Patients

BACKGROUND

Thyroid hormone metabolism is modulated by starvation and overfeeding but also by dietary composition. Unfortunately, little is known about the effect of malnutrition on disease-induced nonthyroidal illness (NTI). In this study, we investigated whether the degree of NTI after surgery differed between severely malnourished and well-fed patients with head and neck cancer.

METHODS

Plasma levels of the thyroid hormones 3',5-triiodothyronine (T(3)), reverse T(3) (rT(3)), free T(4) (FT(4)), and thyrotropin (TSH) were measured on the first day before the operation and on the first, fourth, and seventh day after the operation in 16 malnourished patients who were admitted for intentional curative surgery of T1-T4 carcinomas of the head and neck. Six well-fed head and neck cancer patients eligible for surgical treatment served as a control group.

RESULTS

In the malnourished group, rT(3) showed a significant increase, whereas T(3) and FT(4) decreased significantly due to the operation. TSH showed no significant change. During the postoperative course, it took 7 days until rT(3) and 4 days until T(3) and FT(4) were restored to their preoperative value. In contrast, well-fed patients did not develop NTI.

CONCLUSIONS

This study shows that peri- and postoperative rT(3), T(3), and FT(4) levels change significantly in malnourished patients compared with well-fed patients. Therefore, it can be concluded that nutrition status of patients undergoing major head and neck surgery should be optimized in order to prevent the development of NTI.

Abnormal thyroid hormones and non-thyroidal illness syndrome in obstructive sleep apnea, and effects of CPAP treatment

OBJECTIVE

In obstructive sleep apnea (OSA), while both hypothyroidism and hyperthyroidism have been studied, the occurrence of non-thyroidal illness syndrome (NTIS) (normal thyroid stimulating hormone [TSH] with low triiodotironine) has not been investigated. We explored the occurrence of NTIS in patients with moderate to severe OSA and its relationship to the severity of nocturnal respiratory disorders. We also studied the occurrence of subclinical hypothyroidism (SH, ie, high TSH with normal thyroxine) in OSA and changes in circulating TSH, free triiodotironine (fT3) and free thyroxine (fT4) after CPAP treatment.

METHODS

After a nocturnal respiratory polysomnography, 125 consecutive patients with moderate to severe OSA and 60 control subjects with normal nocturnal respiration were recruited. Morning circulating TSH, fT3, and fT4 were measured in all subjects. In a subsample of patients, nocturnal polysomnography and hormonal determinations were repeated after CPAP treatment for five months.

RESULTS

NTIS was found in 13 (10.4%), and SH in ten (8%) OSA subjects, but not in any control subjects. Patients with NTIS showed worse mean nocturnal oxygen saturation and time with saturation <90% (both p < 0.001). After treatment, NTIS subjects (n = 13) showed an increase in fT3 (p < 0.001) to the normal range, and SH subjects (n = 6) a slight decrease in TSH (p = 0.01). In the patients with normal hormones before treatment (n = 45), no change was observed.

CONCLUSIONS

NTIS may occur in OSA patients with severe nocturnal hypoxemia. OSA treatment is followed by an improvement in TSH in patients with abnormal baseline levels of this hormone, and by recovery of NTIS.

A case of masked toxic adenoma in a patient with non-thyroidal illness

BACKGROUND

Non-thyroidal illness (NTI) refers to changes in thyroid hormone levels in critically ill patients in the absence of primary hypothalamic-pituitary-thyroid dysfunction, and these abnormalities usually resolve after clinical recovery. However, NTI can be accompanied by primary thyroid dysfunction. We report herein a case of a woman with NTI accompanied by primary hyperthyroidism.

CASE PRESENTATION

A 52-year-old female was admitted to the intensive care unit with heart failure and atrial fibrillation. She had a longstanding thyroid nodule, and a thyroid function test revealed low levels of triiodothyronine and free thyroxine as well as undetectable thyroid stimulating hormone (TSH). She was diagnosed with NTI, and her TSH level began to recover but not completely at discharge. The thyroid function test was repeated after 42 months to reveal primary hyperthyroidism, and a thyroid scan confirmed a toxic nodule.

CONCLUSION

This case suggests that although NTI was diagnosed, primary hyperthyroidism should be considered as another possible diagnosis if TSH is undetectable. Thyroid function tests should be repeated after clinical recovery from acute illness.

Thyroid hormones and antioxidant systems: focus on oxidative stress in cardiovascular and pulmonary diseases

In previous works we demonstrated an inverse correlation between plasma Coenzyme Q₁₀ (CoQ₁₀) and thyroid hormones; in fact, CoQ₁₀ levels in hyperthyroid patients were found among the lowest detected in human diseases. On the contrary, CoQ₁₀ is elevated in hypothyroid subjects, also in subclinical conditions, suggesting the usefulness of this index in assessing metabolic status in thyroid disorders. A Low-T3 syndrome is a condition observed in several chronic diseases: it is considered an adaptation mechanism, where there is a reduction in pro-hormone T4 conversion. Low T3-Syndrome is not usually considered to be corrected with replacement therapy. We review the role of thyroid hormones in regulation of antioxidant systems, also presenting data on total antioxidant capacity and Coenzyme Q₁₀. Published studies suggest that oxidative stress could be involved in the clinical course of different heart diseases; our data could support the rationale of replacement therapy in low-T3 conditions.

Short term triiodo-L-thyronine treatment inhibits cardiac myocyte apoptosis in border area after myocardial infarction in rats

Thyroid hormone (TH) levels decline after a myocardial infarction (MI). Treatment with TH has been shown to improve left ventricular (LV) function in MI and other cardiovascular diseases, but the mechanisms are not clear. We have previously shown that TH can prevent myocyte apoptosis via Akt signaling in cultured neonatal rat cardiomyocytes. In this study, the effects of triiodo-L-thyronine (T3) on LV function and myocyte apoptosis after MI was examined in rats. After surgery, MI rats were treated with T3 for 3 days. Compared with sham-operated rats, MI rats showed significantly increased LV chamber dimension during systole and decreased LV function. T3 treatment increased LV +/-dP/dt but did not change LV chamber dimensions. MI rats also showed significantly increased myocyte apoptosis in the border area as assessed by DNA laddering and TUNEL assay. T3 treatment decreased the amount of DNA laddering, and reduced TUNEL positive myocytes in the border area, which was associated with phosphorylation of Akt at serine 473. These results suggest that T3 can protect myocytes against ischemia-induced apoptosis, which may be mediated by Akt signaling.

Perioperative thyroid hormone kinetics in patients undergoing major oral and maxillofacial operations

PURPOSE

The aim of this study was to investigate the perioperative response of serum thyroid hormones in patients who underwent extensive maxillofacial operations with desflurane (0.2 to 1.5 MAC) and remifentanil (0.05 to 0.3 microg/kg/min) anesthesia.

MATERIALS AND METHODS

Serum thyroxine, total and free triiodothyronine, thyroid-stimulating hormone, interleukin-1beta and 6, TNF-alpha, free fatty acids, S100B protein, CRP, as well as amyloid A protein were measured in 13 patients subjected to extensive oral and maxillofacial operations. Samples were collected before anesthesia induction, at the end, and 6, 12, 24, and 72 hours after the end of surgery. Patients during the study fasted, and at the postoperative period received Ringer's saline or with 5% dextrose alternatively, at the rate of 0.5 to 1.5 mL/kg/hr.

RESULTS

Thyroid hormones concentrations showed a significant decrease over time whereas their values recovered to the baseline 72 hours after surgery. Interleukin 1beta, 6, S100B protein, CRP, serum amyloid A protein, and free fatty acids showed a significant increase 6, 12, and 24 hours after the end of the operation as related to the basal value. No significant clinical complications were recorded over the study.

CONCLUSION

Patients undergoing extensive oral and maxillofacial surgery exhibit marked decrease in serum thyroid hormones. Stress response, anesthesia, and perioperative fasting may be decisive factors eliciting this response. These metabolic derangements do not deteriorate the clinical outcome and subsequently may be an adaptive response for energy preservation in various organs.

Non-thyroidal illness syndrome is a manifestation of hypothalamic-pituitary dysfunction, and in view of current evidence, should be treated with appropriate replacement therapies

This article documents the role of hypothalamic hypothyroidism and decreased T4-->T3 conversion as the cause of low T4 and T3 in non-thyroidal illness syndrome (NTIS). This article also presents the arguments for administration of replacement triiodothyronine (T3) and thyroxine (T4) hormone in patients who have NTIS. It is impossible to be certain at this time that it is beneficial to replace hormone, or whether this could be harmful. Only a prospective study will be adequate to prove this point, and probably this would need to involve hundreds of patients. If effective, thyroid hormone replacement will be one of many beneficial treatments given the patient, rather than a single magic bullet, which would reverse all the metabolic changes going wrong in these severely ill patients.

Relationship between circulating cytokine levels and thyroid function following bone marrow transplantation

The relation between thyroid hormone changes and cytokines in bone marrow transplantation (BMT) patients has not been studied. This prospective study was designed to determine the relation between thyroid hormones and cytokine levels after BMT and their effects on the mortality. We studied 80 patients undergoing allogeneic BMT. Serum thyroid hormone parameters and cytokine levels were measured before and serially during 6 months after BMT. Serum T(3) decreased to a nadir 3 weeks post-BMT and serum T(4) was lowest at 3 months post-BMT. Serum thyroid stimulating hormone (TSH) sharply decreased to a nadir at 1 week and recovered. Serum interleukin-6 increased for 2 weeks after BMT and declined thereafter. Serum tumor necrosis factor-alpha increased for 3 weeks after BMT and declined thereafter. After 3 weeks post-BMT, both cytokine levels were negatively correlated with serum T(3) and T(4) levels. A total of 29 patients died before 1 year post-BMT and 51 patients survived longer than 1 year. Those patients who died before 1 year post-BMT had significantly lower levels of T(4) at 3 weeks, 3 and 6 months than surviving patients. In conclusion, increased levels of serum IL-6 and TNF-alpha were negatively correlated with thyroid hormone concentrations in BMT recipients suggesting the role of these cytokines in euthyroid sick syndrome.

Evaluation of metabolic status in amiodarone-induced thyroid disorders: plasma coenzyme Q10 determination

In previous works we have demonstrated that Coenzyme Q10 (CoQ10) levels have a significant inverse correlation with thyroid hormone concentration in patients with spontaneous hyper- or hypothyroidism. In order to verify whether this correlation is maintained in patients on long-term amiodarone therapy, in whom thyroid metabolism is altered by the iodine contained in the drug, we have studied 30 patients with thyroid dysfunction induced by chronic amiodarone treatment. We have distinguished four groups of patients: group A (n = 8): patients with true hyperthyroidism induced by drug administration; group B (n = 11): patients with mild hyperthyroid symptoms, but isolated thyroxine increase or dissociation between different indexes of thyroid function; group C (n = 5): patients with normal thyroid hormone levels, but increased TSH levels; group D (n = 6): patients who appeared really clinically euthyroid, with normal thyroid hormone levels and normal TSH response to TRH. In group A patients, plasma CoQ10 levels averaged 0.49 +/- 0.03 micrograms/ml, significantly lower than those in normal subjects and similar to those observed in spontaneous hyperthyroid patients. In group B patients, CoQ10 levels were in the normal range (0.88 +/- 0.10 microgram/ml). In group C patients, CoQ10 levels were lower than those in normal subjects and similar to those of group A patients (0.49 +/- 0.04 microgram/ml); they differed, in regards to CoQ10 values, in comparison with spontaneous primary hypothyroid patients, who had very high levels of plasma CoQ10. Finally, in group D patients, CoQ10 levels were in the normal range (0.77 +/- 0.04 microgram/ml).(ABSTRACT TRUNCATED AT 250 WORDS)