Changes within the thyroid axis during critical illness

The ageing thyroid: implications for longevity and patient care

Thyroid hormones have vital roles in development, growth and energy metabolism. Within the past two decades, disturbances in thyroid hormone action have been implicated in ageing and the development of age-related diseases. This Review will consider results from biomedical studies that have identified the importance of precise temporospatial regulation of thyroid hormone action for local tissue maintenance and repair. Age-related disturbances in the maintenance of tissue homeostasis are thought to be important drivers of age-related disease. In most iodine-proficient human populations without thyroid disease, the mean, median and 97.5 centile for circulating concentrations of thyroid-stimulating hormone are progressively higher in adults over 80 years of age compared with middle-aged (50-59 years) and younger (20-29 years) adults. This trend has been shown to extend into advanced ages (over 100 years). Here, potential causes and consequences of the altered thyroid status observed in old age and its association with longevity will be discussed. In about 5-20% of adults at least 65 years of age, thyroid-stimulating hormone concentrations are elevated but circulating concentrations of thyroid hormone are within the population reference range, a condition referred to as subclinical hypothyroidism. Results from randomized clinical trials that have tested the clinical benefit of thyroid hormone replacement therapy in older adults with mild subclinical hypothyroidism will be discussed, as well as the implications of these findings for screening and treatment of subclinical hypothyroidism in older adults.

The role of hormones in sepsis: an integrated overview with a focus on mitochondrial and immune cell dysfunction

Sepsis is a dysregulated host response to infection that results in life-threatening organ dysfunction. Virtually every body system can be affected by this syndrome to greater or lesser extents. Gene transcription and downstream pathways are either up- or downregulated, albeit with considerable fluctuation over the course of the patient's illness. This multi-system complexity contributes to a pathophysiology that remains to be fully elucidated. Consequentially, little progress has been made to date in developing new outcome-improving therapeutics. Endocrine alterations are well characterised in sepsis with variations in circulating blood levels and/or receptor resistance. However, little attention has been paid to an integrated view of how these hormonal changes impact upon the development of organ dysfunction and recovery. Here, we present a narrative review describing the impact of the altered endocrine system on mitochondrial dysfunction and immune suppression, two interlinked and key aspects of sepsis pathophysiology.

Subclinical hypothyroidism is associated with basal ganglia enlarged perivascular spaces and overall cerebral small vessel disease load

Background

The association between subclinical hypothyroidism (SCH) and cerebral small vessel disease (CSVD) in the stroke-free population is currently unclear.

Methods

A total of 354 individuals without a history of stroke were enrolled in this study. Demographic data, medical history, vascular risk factors, carotid arteriosclerosis, and the results of laboratory tests were collated. SCH is defined as an elevation in thyroid-stimulating hormone levels, but with normal free thyroxine levels. Magnetic resonance imaging (MRI) was used to assess 4 markers of CSVD, including white matter hyperintensities (WMHs), lacunes, deep microbleeds, and enlarged perivascular spaces (EPVSs). The overall CSVD load was then ranked using an ordinal scale ranging from 0 to 4. Brain atrophy was measured semi-quantitatively on MRI. A binary logistic regression model was used to explore the association of SCH with each CSVD marker after adjusting for confounding factors. The ordinal regression model was used to explore the association of SCH with CSVD burden and brain atrophy after adjusting for confounding factors.

Results

The mean age of the participants (66.9% males) was 69.4±12.8 years. SCH was observed in 44 (12.4%) participants. MRI findings revealed 13% of cases with lacunes, 6.2% with microbleeds, 50.3% with confluent WMH, and 49.2% with extensive basal ganglia EPVS. Assessment of total CSVD burden showed that 29.1% scored 1, 30.5% scored 2, 6.5% scored 3, and 2.3% scored ≥3. SCH was associated with extensive basal ganglia EPVS [odds ratio (OR) =2.175; 95% confidence interval (CI): 1.075 to 4.401] and total CSVD load (OR =1.879; 95% CI: 1.028 to 3.438). SCH was not associated with advanced brain atrophy.

Conclusions

SCH is associated with the advanced total burden of CSVD and basal ganglia EPVS in the stroke-free population.

Sepsis as a Pan-Endocrine Illness-Endocrine Disorders in Septic Patients

Sepsis is defined as "life-threatening organ dysfunction caused by a dysregulated host response to infection". One of the elements of dysregulated host response is an endocrine system disorder. Changes in its functioning in the course of sepsis affect almost all hormonal axes. In sepsis, a function disturbance of the hypothalamic-pituitary-adrenal axis has been described, in the range of which the most important seems to be hypercortisolemia in the acute phase. Imbalance in the hypothalamic-pituitary-thyroid axis is also described. The most typical manifestation is a triiodothyronine concentration decrease and reverse triiodothyronine concentration increase. In the somatotropic axis, a change in the secretion pattern of growth hormone and peripheral resistance to this hormone has been described. In the hypothalamic-pituitary-gonadal axis, the reduction in testosterone concentration in men and the stress-induced "hypothalamic amenorrhea" in women have been described. Catecholamine and β-adrenergic stimulation disorders have also been reported. Disorders in the endocrine system are part of the "dysregulated host response to infection". They may also affect other components of this dysregulated response, such as metabolism. Hormonal changes occurring in the course of sepsis require further research, not only in order to explore their potential significance in therapy, but also due to their promising prognostic value.

Sepsis therapies: learning from 30 years of failure of translational research to propose new leads

Sepsis has been identified by the World Health Organization (WHO) as a global health priority. There has been a tremendous effort to decipher underlying mechanisms responsible for organ failure and death, and to develop new treatments. Despite saving thousands of animals over the last three decades in multiple preclinical studies, no new effective drug has emerged that has clearly improved patient outcomes. In the present review, we analyze the reasons for this failure, focusing on the inclusion of inappropriate patients and the use of irrelevant animal models. We advocate against repeating the same mistakes and propose changes to the research paradigm. We discuss the long-term consequences of surviving sepsis and, finally, list some putative approaches-both old and new-that could help save lives and improve survivorship.

Prognostic value of subclinical thyroid dysfunction in ischemic stroke patients treated with intravenous thrombolysis

Data regarding the association between subclinical thyroid dysfunction and clinical outcomes in ischemic stroke patients with intravenous thrombolysis (IVT) are limited. We aimed to investigate the predictive value of subclinical thyroid dysfunction in END, functional outcome and mortality at 3 months among IVT patients. We prospectively recruited 563 IVT patients from 5 stroke centers in China. Thyroid function status was classified as subclinical hypothyroidism, subclinical hyperthyroidism (SHyper) and euthyroidism. The primary outcome was END, defined as ≥ 4 point in the NIHSS score within 24 h after IVT. Secondary outcomes included 3-month functional outcome and mortality. Of the 563 participants, END occurred in 14.7%, poor outcome in 50.8%, and mortality in 9.4%. SHyper was an independent predictor of END [odd ratio (OR), 4.35; 95% confidence interval [CI], 1.86–9.68, P = 0.003], 3-month poor outcome (OR, 3.24; 95% CI, 1.43–7.33, P = 0.005) and mortality [hazard ratio, 2.78; 95% CI, 1.55–5.36, P = 0.003]. Subgroup analysis showed that there was no significant relationship between SHyper and clinical outcomes in IVT patients with endovascular therapy. In summary, SHyper is associated with increased risk of END, and poor outcome and mortality at 3 months in IVT patients without endovascular therapy.

Prognostic Value of Thyroid Profile in Critical Care Condition

BACKGROUND

Patients suffering from critical illness admitted to the Intensive Care Unit (ICU) exhibit alterations in their thyroid hormone levels, collectively termed as euthyroid sick syndrome or nonthyroidal illness syndrome. Our study was conducted to determine the correlation between these changes in thyroid hormone levels and the prognosis of ICU-admitted patients.

METHODS

A total of 270 ICU-admitted patients without previous history of thyroid disorder were included in the study. We recorded their baseline characteristics, acute physiology and chronic health evaluation (APACHE-II) score, thyroid hormone levels, lactate, and other parameters on admission. ICU mortality was the primary outcome. We analyzed the ability of each parameter to predict mortality in the participants. Further, we also evaluated whether the combination of thyroid hormone levels with APACHE-II score could improve the mortality prediction.

RESULTS

The mean age of the study population was 38.99 ± 18.32 years. A total of 81 patients (30%) expired during their ICU treatment. Both fT3 and fT4 levels were lower in nonsurvivors compared to survivors. Among the thyroid hormones, fT3 had the highest predictive value for ICU mortality, as seen by the largest area under the curve (AUC) value (0.990 ± 0.007) which was even greater than AUC of APACHE-II score (0.824 ± 0.051) and fT4 (0.917 ± 0.049). Univariate logistic regression analysis showed that fT3 (β = 140.560) had the highest predictive potential for ICU mortality compared with APACHE-II score (β = 0.776), fT4 (β = 17.62) and other parameters. Multivariate logistic regression analysis revealed that the combination of fT3 and APACHE-II (R² = 0.652) was superior in predicting mortality than APACHE-II alone (R² = 0.286).

CONCLUSION

We observed that fT3 was the strongest predictor of ICU mortality compared to all other parameters included in our study. Further, the combination of fT3 levels and APACHE-II scores provided for a higher probability for predicting mortality in ICU patients.

Subclinical hypothyroidism and risk of cerebral small vessel disease: A hospital-based observational study

OBJECTIVE

Subclinical hypothyroidism (SCH) has been associated with atherosclerosis and increased risk of ischaemic stroke. However, whether SCH is associated with cerebral small vessel disease (cSVD) remains largely unexplored. This study aimed to investigate the relationship between SCH and total cSVD burden, a composite measurement detected with magnetic resonance imaging (MRI), in patients with minor ischaemic stroke or transient ischaemic attack (TIA).

DESIGN

This was a prospective observational cohort study conducted in a tertiary referral hospital.

METHODS

Subclinical hypothyroidism (SCH) was defined as with mildly or moderately increased thyroid-stimulating hormone levels (TSH, 4.5-10.0 mIU/L), but with normal free thyroxine levels. Brain MRI presence of silent lacunar infarcts (LIs), white matter lesions (WMLs), cerebral microbleeds (CMBs) and enlarged perivascular spaces (EPVs) were summed to a validated scales ranging from 0 to 4 to represent the load of cSVD. The associations between SCH and cSVD were analysed by logistic regression analyses.

RESULTS

Subclinical hypothyroidism (SCH) was identified in 43 of 229 (18.8%) patients with minor stroke or TIA. Compared with patients without SCH, those with SCH had higher risks of WMLs, CMBs and total cSVD burden. Adjustment of potential confounders did not change these associations.

CONCLUSIONS

These findings showed that SCH might be associated with the presence of WMLs, CMBs, as well as cSVD burden in patients with minor stroke or TIA.

Endocrine and Metabolic Alterations in Sepsis and Implications for Treatment

Sepsis induces profound neuroendocrine and metabolic alterations. During the acute phase, the neuroendocrine changes are directed toward restoration of homeostasis, and also limit unnecessary energy consumption in the setting of restricted nutrient availability. Such changes are probably adaptive. In patients not recovering quickly, a prolonged critically ill phase may ensue, with different neuroendocrine changes, which may represent a maladaptive response. Whether stress hyperglycemia should be aggressively treated or tolerated remains a matter of debate. Until new evidence from randomized controlled trials becomes available, preventing severe hyperglycemia is recommended. Evidence supports withholding parenteral nutrition in the acute phase of sepsis.

THYROID AND AGING

OBJECTIVE

Review physiologic thyroid function changes with aging and emphasize careful interpretation of tests in the aging population.

METHODS

Literature review.

RESULTS

Using age-specific thyroid-stimulating hormone (TSH) reference ranges should minimize or avoid the unnecessary diagnosis of thyroid disease in elderly patients. Subclinical thyroid dysfunction and abnormal TSH with normal thyroid levels may improve with time, so careful monitoring of thyroid function is recommended. Overt thyroid disease should always be treated.

CONCLUSION

Clinical judgement is always warranted to decide how and when to treat subclinical thyroid disease in the elderly.

ABBREVIATIONS

FT4 = free thyroxine; rT3 = reverse triiodothyronine; T3 = triiodothyronine; T4 = thyroxine; TFT = thyroid function test; TSH = thyroid-stimulating hormone.

Triiodothyronine Administration in a Model of Septic Shock: A Randomized Blinded Placebo-Controlled Trial

OBJECTIVES

Triiodothyronine concentration in plasma decreases during septic shock and may contribute to multiple organ dysfunction. We sought to determine the safety and efficacy of administering triiodothyronine, with and without hydrocortisone, in a model of septic shock.

DESIGN

Randomized blinded placebo-controlled trial.

SETTING

Preclinical research laboratory.

SUBJECTS

Thirty-two sheep rendered septic with IV Escherichia coli and receiving protocol-guided sedation, ventilation, IV fluids, and norepinephrine infusion.

INTERVENTIONS

Two hours following induction of sepsis, 32 sheep received a 24-hour IV infusion of 1) placebo + placebo, 2) triiodothyronine + placebo, 3) hydrocortisone + placebo, or 4) triiodothyronine + hydrocortisone.

MEASUREMENTS AND MAIN RESULTS

Primary outcome was the total amount of norepinephrine required to maintain a target mean arterial pressure; secondary outcomes included hemodynamic and metabolic indices. Plasma triiodothyronine levels increased to supraphysiological concentrations with hormonal therapy. Following 24 hours of study drug infusion, the amount of norepinephrine required was no different between the study groups (mean ± SD μg/kg; placebo + placebo group 208 ± 392; triiodothyronine + placebo group 501 ± 370; hydrocortisone + placebo group 167 ± 286; triiodothyronine + hydrocortisone group 466 ± 495; p = 0.20). There was no significant treatment effect on any hemodynamic variable, metabolic parameter, or measure of organ function.

CONCLUSIONS

A 24-hour infusion of triiodothyronine, with or without hydrocortisone, in an ovine model of septic shock did not markedly alter norepinephrine requirement or any other physiological parameter.

Thyroid hormones in extreme longevity

The aim of the present review was to summarize knowledge about thyroid hormones (THs) and longevity. Longevity is a complex multifactorial phenomenon on which specific biological pathways, including hormonal networks involved in the regulation of homeostasis and survival, exert a strong impact. THs are the key responsible for growth, metabolism rate and energy expenditure, and help in maintaining cognition, bone and cardiovascular health. THs production and metabolism are fine tuned, and may help the organism to cope with a variety of environmental challenges. Experimental evidence suggests that hypothyroid state may favor longevity by reducing metabolism rate, oxidative stress and cell senescence. Data from human studies involving healthy subjects and centenarians seem to confirm this view, but THs changes observed in older patients affected by chronic diseases cannot be always interpreted as a protective adaptive mechanism aimed at reducing catabolism and prolonging survival. Medications, selected chronic diseases and multi-morbidity can interfere with thyroid function, and their impact is still to be elucidated.

Sepsis leads to thyroid impairment and dysfunction in rat model

Sepsis was a systemic response to a local infection. Apoptosis was observed in the experimental sepsis. In this study, cecal ligation and puncture (CLP)-induced sepsis was established in rats. We found that sepsis decreased thyroid hormone levels, including triiodothyronine (T3), thyroxine (T4), free T3 (fT3), and free T4 (fT4). Besides, we detected the increasing expression level of Caspase-3 and increasing ratio of TUNEL positive cells in the thyroid after sepsis. Furthermore, a series of pathological ultrastructural changes were observed in thyroid follicular epithelial cells by CLP-induced sepsis. This study established a sepsis animal model and provided the cellular and molecular basis for decoding the pathological mechanism in thyroid with the occurrence of sepsis.

Genetic abnormalities in thyroid hormone deiodinases

PURPOSE OF REVIEW

The purpose of this study was to review several of the most recent and most important clinical studies regarding the effects of how genetic variation in the deiodinases can influence health.

RECENT FINDINGS

Common variation in DIO1 but not DIO2 or DIO3 is robustly associated with thyroid hormone levels at genome-wide levels of significance although the effect is modest. There is growing evidence that common variation in DIO2, particularly the Thr92Ala substitution, is associated with important clinical endpoints including osteo-arthritis and intelligence quotient; however, the mechanism of action appears to vary between tissues with several unexpected pathways recently being elucidated including effects on Golgi function and DNA methylation. In addition, there is emerging evidence of interaction with iodine and thyroid status.

SUMMARY

The clinical importance of genetic variation in the deiodinases has yet to be fully elucidated and their impact is likely to vary between individuals and body systems dependent on multiple factors within tissues and coexistent diseases and environmental factors. Exploration of whether there are rare functional variants in the deiodinases is now possible in population studies, which may yield greater insight in the near future. Studies of the impact of genetic variation in the deiodinases in individuals with iodine deficiency, subclinical thyroid disease, or those on levothyroxine are urgently needed.

Alterations in Thyroid Hormones Due to Increased Intraabdominal Pressure in Rats

PURPOSE

Although the effects of increased intraabdominal pressure on the abdominal organs are well known, there is a limited data regarding its effects on the thyroid hormones. The aim of this study is to investigate the changes in thyroid hormone profiles during stress endocrine response induced by increased intraabdominal pressure, which was obtained by pneumoperitoneum in rats.

MATERIALS AND METHODS

A hundred-fifty female wistar albino rats were divided into three main groups, according to intraabdominal pressure applied; Control (Group 1), (n:30), low pressure, 15 mmHg, (Groups 2 and 3), (n:60), and high intraabdominal pressure, 25 mmHg, (Groups 4 and 5), (n:60) groups. Groups 2, 3, 4, 5 were divided into three subgroups separately, according to duration of intraabdominal pressure. Rats in Groups 3 and 5 were decompressed at the end of times indicated (15th, 30th, and 45th min) and blood samples were obtained. Whereas blood samples from Groups 2 and 4 were drawn without decompression at the end of times indicated. Measurements included thyroid stimulating hormone, cortisole, vasopressin, adrenocorticotropic hormone, triiodotronin and thyroxin.

RESULT

Our study revealed that blood TSH levels reduce and free T3 and T4 levels increase in case of prolonged intraabdominal pressure increase that cause abdominal compartment syndrome. The change in blood thyroid hormone levels are encountered prominently on 30th and 45th min.

CONCLUSION

Secretion of vasopressin, adrenocorticotropic Hormone and cortisol increases with increasing intraabdominal pressure. At high pressures, thyroid stimulating hormone secretion decreases while the secretion of triiodotronin increases. The effect of this case on the clinical findings has not been fully clarified yet and it needs further studies to clarify underlying mechanism. In this perspective, the findings of this study may be used in further clinical and experimental studies.

Importance of specific reference values for evaluation of the deteriorating thyroid function in patients with end-stage renal disease on hemodialysis

BACKGROUND/AIM

We evaluated the thyroid function in end-stage renal disease (ESRD) on maintenance hemodialysis.

MATERIAL/METHODS

Thyroid function and clinical hypothyroid score were evaluated in 145 ESRD patients.

RESULTS

Comparison of thyroid function between 127 ESRD patients, excluding 18 patients with suppressed or elevated serum TSH level, and age/sex-matched healthy controls (76 in midlife group aged under 65 and 51 in late-life group aged 65 or over) using a multivariate logistic regression analysis suggested significant difference (P < 0.0001), mainly in serum fT4 level (P = 0.0099) and age (P = 0.0492), but not in serum fT3 (not significant; ns), TSH (ns) level or fT3/fT4 ratio (ns). Serum fT3 level and fT3/fT4 ratio were significantly lower (P < 0.001) in late-life group only in ESRD. Reference values calculated for midlife ESRD patients, such as 0.6-1.3 ng/dl for fT4 compared with 0.8-1.7 ng/dl for healthy control, were helpful for the diagnosis of mild but definite hyperthyroidism in whom serum fT4 level was 1.5 ng/dl. The prevalence of primary thyroid dysfunction, compared with the values for ESRD, was 0.7 % for hyperthyroidism, 1.4 % for overt hypothyroidism and 10.3 % for subclinical hypothyroidism. Hypothyroid score was high among those with ESRD independent of thyroid dysfunction.

CONCLUSIONS

Serum fT4 level was markedly lower without a change in fT3/fT4 ratio in ESRD. This may suggest typical carbohydrate-sufficient non-thyroidal illness. The specific reference values for ESRD were useful to evaluate borderline thyroid dysfunction and to evaluate the prevalence of the patients with primary thyroid dysfunction in ESRD.

Evaluation of serum thyroid hormones in dogs with systemic inflammatory response syndrome or sepsis

OBJECTIVE

To determine whether dogs with systemic inflammatory response syndrome (SIRS) or sepsis have derangements in serum thyroid hormone concentrations and to evaluate whether such derangements relate to illness severity or outcome.

DESIGN

Prospective observational study. Dogs hospitalized with SIRS or sepsis between May and December 2010 were included. Serum thyroid hormone concentrations were measured in all dogs. Data obtained on admission were used to calculate the Acute Patient Physiologic and Laboratory Evaluation (APPLE) scores.

SETTING

University teaching hospital.

ANIMALS

Twenty-two consecutive client-owned dogs hospitalized with SIRS or sepsis were enrolled; 18 dogs completed the study and 4 dogs were excluded for incomplete data. Forty-nine healthy dogs owned by volunteers were used as controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Decreased total thyroxine (TT4) concentrations were documented in all septic and 7/9 dogs with SIRS. Free T4 concentrations were decreased, but were within the reference interval in 12/18 dogs with SIRS or sepsis compared to control dogs (P < 0.001). Dogs with increased APPLE(fast) scores were less likely to survive (P = 0.017).

CONCLUSIONS

Dogs with SIRS or sepsis have derangements in measured serum thyroid hormones. No relationships were identified between thyroid hormone concentrations and survival. The APPLE(fast) score was the only variable predictive of poor outcome.

Two patients with atypical low triiodothyronine syndrome: primary deiodinase abnormalities?

Low triiodothyronine (T₃) concentrations in the presence of normal thyroxine (T₄) and TSH levels, referred to as the low T₃ syndrome (LT₃S), are common. LT₃S may be caused by starvation, various non-thyroidal illnesses (NTIs) and some medications. Reverse T₃ (rT₃) concentrations are elevated in the more severely ill, and they characteristically fail to respond to exogenous levothyroxine (l-T₄) therapy. The biochemical abnormalities have been explained on the basis of altered peripheral deiodinase activities. Herein, we report on two patients with hypothyroid symptoms who on testing were found to have LT₃S. They were atypical clinically in not having LT₃S due to any of the usual causes, had no increased rT₃ concentrations, and had a normal negative TSH feedback response to l-T₄. One (patient 1) had previously been diagnosed with Hashimoto's autoimmune primary hypothyroidism and was on l-T₄ therapy. Both had T₄ concentrations in the reference range. TSH levels were elevated in patient 1 and in the reference range in patient 2. Starting or increasing l-T₄ doses resulted in no clinical improvement and no increase in T₃ levels in spite of a marked increase in T₄ levels. It is suggested that in the absence of the usual causes, lack of elevated rT₃ levels, response to treatment and intact negative TSH feedback these two patients differ from the usual secondary causes of decreases in deiodinase activity. It is speculated that they may represent primary alterations in deiodinase enzymes possibly due to genetic variations in the deiodinase-encoding genes.

Thyroid disorders in older adults

This article summarizes the current literature about serum thyroid parameters and thyroid disease during aging. Changes in thyroid function tests may be part of the physiology of aging, after exclusion of confounding variables. Overt thyroid disease requires immediate treatment. Treatment of subclinical hyperthyroidism in the elderly can be advocated, while watchful waiting may be an appropriate approach for subclinical hypothyroidism.

The influence of liver and pancreas surgery on the thyroid function

Background

Nowadays, the increasing number of oncologic patients with liver or pancreatic tumours are subjected to surgical treatment, as it can provide a long-term survival or sometimes cure. As a result, numerous new clinical questions regarding metabolic disturbances in these patients have been arisen. Among others, the impact of the pancreas and liver surgery extent in relation to the thyroid function remains to be elucidated.

Materials and methods

The study comprised 51 patients (25 men and 26 women, mean age ± SD 61.6 ± 10.4 yrs, mean ± SD) with pancreatic or liver tumours, qualified for abdominal operation. Serum levels of FT3, FT4 and TSH were measured on the day before (time “0”) and on the 1^st, 3^rd and 5^th day after surgery in two (2) subgroups reflecting the extent of surgery: twenty seven (27) patients (14 men and 13 women, mean age ± SD 61.5 ± 11.8 yrs) after major surgery (Whipple’s surgery, right and left hemihepatectomy, segmentectomy of the liver, distal pancreatectomy, total duodenopancreatectomy) and twenty four (24) patients (11 men and 13 women, mean age ± SD 61.8 ± 8.9 yrs) after minor, palliative surgery (exploratory laparotomy, gastroenterostomy, triple by-pass, liver tumour embolization, hepaticojejunostomy). Additionally, the obtained results were analyzed in relation to the type of the disease (pancreatic surgery vs liver surgery).

Results

Mean serum FT3 level decreased significantly during the study in major and minor surgery subgroups (p<0.001, in both) in comparison to the baseline values, accompanied by stable serum concentrations of TSH (NS) and FT4 (NS). The above decreasing tendency in FT3 concentrations was similar in both subgroups (NS), the same as were unchanged levels of TSH (NS) and FT4 (NS). Mean FT4 concentration on the 3^rd and 5^th day after major surgery was lower in pancreatic tumour patients in comparison to liver tumour patients (p=0.002, p=0.032, respectively). Similarly, mean FT3 concentration on the 3^rd day in minor surgery subgroup was lower in pancreatic tumour patients in comparison to liver tumour patients (p=0.015).

Discussion

Our findings have confirmed essential reduction of FT3 values after abdominal surgery, independently of surgery extent. Additionally, pancreatic tumour patients are more likely to have lower FT3 and FT4 levels after surgery when compared to liver tumour patients.

Thyroid function and stress hormones in children with stress hyperglycemia

The purpose of the study is to determine the prevalence of stress hyperglycemia and to investigate how thyroid and stress hormones alter during stress hyperglycemia in children admitted to pediatric emergency wards. A prospective cross-sectional study was conducted in children, less than 19 years old, who were admitted to pediatric emergency wards of Nemazee and Dastgheib Hospitals, Shiraz, Southern Iran. Those patients taking steroids, beta-agonists or intravenously administered glucose before venipuncture, and patients with diabetes mellitus (DM) or thyroid diseases were excluded. Children with blood glucose ≥ 150 mg/dL during admission were regarded as cases. The controls were age- and- sex- matched, euglycemic children. Stress hormones including cortisol, insulin, growth hormone, and prolactin were measured, and thyroid function was tested with a radioimmunoassay (RIA) method in all cases and controls. The results showed that among 1,054 screened children, 39 cases (3.7 %) had stress hyperglycemia and 89 controls were included in the study. The occurrence of hyperglycemia was independent of sex, but it occurred mostly in children under 6 years old. Hyperglycemia occurred more frequently in patients with a positive family history of DM (odds ratio = 3.2, 95 % CI = 1.3-7.9, and P = 0.009). There were no significant differences between cases and controls regarding any hormones except higher cortisol, and lower total T3 and T4 in cases compared with controls. Neither of cases developed diabetes in the 24-month follow-up period. These findings led us to the conclusion that stress hyperglycemia is occasionally seen in critically ill patients. Among the stress hormones measured, only cortisol increased during hyperglycemia. It seems that hyperglycemia is not an important risk factor for future diabetes.

Approach to and treatment of thyroid disorders in the elderly

Thyroid gland dysfunction is prevalent in older adults and may be associated with significant morbidity if misdiagnosed and left untreated. Because of a decreased number of symptoms at presentation, an increased susceptibility to adverse events if not treated, and a greater likelihood of harm from treatment, the diagnosis and management of thyroid disorders in older adults can be challenging. This review focuses on the epidemiology, clinical presentation, risks and complications, and management of thyroid disorders in older adults, including hyperthyroidism, hypothyroidism, thyroid nodules, and thyroid cancer.

Consumptive hypothyroidism resulting from hepatic vascular tumors in an athyreotic adult

CONTEXT

Consumptive hypothyroidism is a rare syndrome resulting from increased catabolism of T(4) and T(3) by increased type 3 iodothyronine deiodinase (D3) activity. Consumptive hypothyroidism has primarily been described as a paraneoplastic syndrome in infants as well as in two adults with D3-expressing tumors.

OBJECTIVE

The aim of the study was to report the third case of consumptive hypothyroidism in an adult and the first in an athyreotic patient.

DESIGN, SETTING, AND PATIENT

We present a 38-yr-old athyreotic female who was euthyroid on a stable therapeutic dose of thyroid hormone for many years and then developed marked hyperthyrotropinemia, coincident with the discovery of large D3-expressing hepatic vascular tumors. The patient also had low serum T(3) and elevated serum rT(3). Hyperthyrotropinemia transiently worsened after surgical resection of the vascular tumors and then persisted for 3 wk after the operation, despite further increases in levothyroxine therapy.

INTERVENTION

The patient's vascular tumor and adjacent normal liver parenchyma were probed with a polyclonal antibody directed against D3.

MAIN OUTCOME MEASURES AND RESULTS

D3 immunostaining of the patient's vascular tumor was positive, with no significant immunoreactivity in the adjacent normal hepatic tissue.

CONCLUSIONS

This is the third case report of consumptive hypothyroidism in an adult and the first in an athyreotic individual. This case demonstrates that hyperthyrotropinemia may persist after partial liver resection, possibly from the hepatic resection itself.

Understanding, recognizing, and managing chronic critical illness syndrome

PURPOSE

No evidence-based guidelines exist for the care of patients with chronic critical illness syndrome (CCIS), a growing population of patients being cared for by nurse practitioners (NPs). The purpose of this article is to provide NPs with a beginning physiological framework, allostasis, to guide their understanding and management of patients with CCIS.

DATA SOURCES

Scientific publications, related clinical guidelines.

CONCLUSIONS

Patients with CCIS are a distinct group of critically ill patients whose care needs are different from those of patients who are acutely critically ill. These patients demonstrate widespread tissue and organ damage. The widespread tissue and organ damage results in a syndrome of interrelated elements, which include neuroendocrine problems, severe malnutrition, wounds, infections, bone loss, polyneuropathy and myopathy, delirium and depression, and suffering.

IMPLICATIONS FOR PRACTICE

In caring for patients with CCIS, NPs need to focus on treating the elements of the syndrome as a cohort of interrelated elements and on re-establishing normalcy for the patient.

Bone physiology and therapeutics in chronic critical illness

Modern medical practices allow patients to survive acute insults and be sustained by machinery and medicines for extended periods of time. We define chronic critical illness as a later stage of prolonged critical illness that requires tracheotomy. These patients have persistent elevations of inflammatory cytokines, diminished hypothalamic-pituitary function, hypercatabolism, immobilization, and malnutrition. The measurement of bone turnover markers reveals markedly enhanced osteoclastic bone resorption that is uncoupled from osteoblastic bone formation. We review the mechanisms by which these factors contribute to the metabolic bone disease of chronic critical illness and suggest potential therapeutics.

Favorable influence of subclinical hypothyroidism on the functional outcomes in stroke patients

Subclinical hypothyroidism (SCH) is thought to have an influence on stroke outcomes. However, few reports demonstrate a favorable relationship between the two. We evaluated this association in acute ischemic stroke. From Jan 2005 to June 2008, 756 acute ischemic stroke patients were recruited within seven days of onset. The patients with overt hypothyroidism/hyperthyroidism or other medical conditions that may affect thyroid function were excluded. Thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels were measured within two days. Patients were divided into two groups: the SCH group (TSH > 5.0 microU/mL and normal FT4 levels) and the control group. Stroke outcomes were assessed using two different criteria. In the first outcome model, favorable outcomes [I] were simply defined by modified Rankin Scale (mRS) scores (<or= 1), while the favorable outcomes [II] were defined as follows: a) a mRS score of 0, if the baseline National Institute of Health Stroke Scale (NIHSS) scores were < 8, b) a mRS score of 0 or 1, if the NIHSS scores were 8-14, c) a mRS score 0-2, if the NIHSS scores were >14. The changes in mRS scores and the proportion of patients with favorable outcomes [I] or [II] at the 30(th) and 90(th) day were compared between the two patient groups. Of the 756 patients, 31 (4.1%) were patients with SCH. More patients from the SCH group showed improvement in NIHSS scores on the 30(th) day compared to the control group (48.4% vs. 25.3%, p=.006). In addition, the proportion of patients who exhibited favorable outcomes [I] was significantly higher in the SCH group on the 90(th) day (74.2% vs. 55.3%, p=.027) and that trend was seen as early as the 30(th) day (p=.102). Similarly, the proportion of the patients with favorable outcomes [II] was significantly greater in the SCH group both on the 30(th) (29.0% vs. 14.6%, p=.039) and 90(th) day (58.0% vs. 31.0%, p=.003). We found that acute ischemic stroke patients with SCH at admission were more likely to show favorable functional outcomes than those without SCH. We can suggest preconditioning before the stroke combined with a reduced response to stress as a possible protective mechanism.

Thyroid hormone therapy for obesity and nonthyroidal illnesses: a systematic review

CONTEXT

Thyroid hormone therapy to enhance weight loss in obesity during caloric deprivation and to improve morbidity and mortality in adults with nonthyroidal illnesses remains controversial.

OBJECTIVE

The aim of this study was to conduct a systematic review evaluating effectiveness and risks of T(3) and/or T(4) therapy in these populations.

DATA SOURCES

Electronic databases and reference lists were searched.

STUDY SELECTION

Studies with comparable control groups comparing T(3) and/or T(4) therapy to placebo in randomized controlled trials (RCTs) or prospective observational studies were selected.

DATA EXTRACTION

Three reviewers performed serial abstraction.

DATA SYNTHESIS

During caloric deprivation of obese subjects, T(3) therapy decreased serum TSH and T(4) concentrations. Consistent effects of T(3) or T(4) on weight loss, protein breakdown, metabolic rate, and heart rate could not be established. In euthyroid cardiac patients, T(3) decreased TSH and free T(4) levels, without consistent effects of T(3) or T(4) on heart rate, cardiac output, or systemic vascular resistance. Mortality increased 3.3-fold with T(4) therapy in acute renal failure patients, whereas an effect in cardiac, critically ill, and burn patients could not be established. Equivalence testing indicated that larger RCTs are required to determine whether thyroid hormone therapy alters end-points in obesity or nonthyroidal illnesses.

LIMITATIONS

Numbers of usable unique studies were small, numbers of patients in each study were inadequate, end-points were variable, few RCTs were performed, and study quality of non-RCTs was poor.

CONCLUSIONS

Available data are inconclusive regarding effectiveness of thyroid hormone therapy in treating obesity or nonthyroidal illnesses, whereas data support that such therapy induces subclinical hyperthyroidism.

Thyroid Function and Cognition during Aging

We summarize here the studies examining the association between thyroid function and cognitive performance from an aging perspective. The available data suggest that there may be a continuum in which cognitive dysfunction can result from increased or decreased concentrations of thyroid hormones. Clinical and subclinical hypothyroidism as well as hyperthyroidism in middle-aged and elderly adults are both associated with decreased cognitive functioning, especially memory, visuospatial organization, attention, and reaction time. Mild variations of thyroid function, even within normal limits, can have significant consequences for cognitive function in the elderly. Different cognitive deficits possibly related to thyroid failure do not necessarily follow a consistent pattern, and L-thyroxine treatment may not always completely restore normal functioning in patients with hypothyroidism. There is little or no consensus in the literature regarding how thyroid function is associated with cognitive performance in the elderly.

Regulation of tissue iodothyronine deiodinase activity in a model of prolonged critical illness

BACKGROUND

The low plasma triiodothyronine (T3) observed during prolonged critical illness can be explained in part by suppressed hepatic deiodinase type I (D1) and increased D3 activity. Infusion of thyrotropin-releasing hormone (TRH) can restore D1 and D3 activity in critically ill rabbits, but it remains unknown whether this is a direct effect of TRH or the TRH-induced rise in circulating thyroxine (T4) and T3.

METHODS

To answer this specific question, burn-injured rabbits randomly received a 4-day treatment with saline, T4, T3, T4+T3, or TRH, started on day 4 of the illness. Plasma iodothyronine concentrations, D1 and D3 activity, and T3-responsive gene expression were quantified in liver and kidney.

RESULTS

Infusion of T4, T3, or TRH increased circulating T3 levels and hepatic D1 activity. Co-infusion of T3 with T4 enhanced T4 to T3 conversion as demonstrated by lower T4, higher T3, and lower reverse T3 (rT3) levels and tended to further increase hepatic D1 activity. Hepatic D1 activity correlated positively with circulating T3 and the T3/rT3 ratio, but not with T4, rT3, or thyroid-stimulating hormone.

CONCLUSIONS

During prolonged critical illness, D1 activity is primarily regulated via changes in circulating T3, suggesting that the low plasma T3 concentrations may be important in sustaining low D1 activity in this condition.

Serum thyrotropin, thyroxine and free thyroxine concentrations as predictors of mortality in critically ill puppies with parvovirus infection: a model for human paediatric critical illness?

This prospective case-controlled study investigated the role of the pituitary-thyroidal axis in the prediction of mortality in dogs. Serum thyrotropin, thyroxine and free thyroxine were measured at admission and daily until death or discharge in dogs ill with parvoviral diarrhoea. Serum thyroxine and free thyroxine in ill dogs were significantly lower than in controls and also significantly lower in nonsurvivors than in survivors on days 1-4. Serum thyrotropin at admission in ill dogs was similar to controls, but was significantly higher in nonsurvivors than in survivors. Thyrotropin concentrations became significantly lower in nonsurvivors vs survivors by day 4.

Thyroid hormone abnormalities and outcome in dogs with non-thyroidal illness

OBJECTIVES

To document thyroid hormone abnormalities in dogs with non-thyroidal illness and identify markers of prognostic value.

METHODS

Circulating total and free thyroxine, total triiodothyronine and thyrotropin concentrations were measured in 196 dogs with non-thyroidal illness. Clinical signs, previous medications and outcome were recorded in each case. Data were analysed to determine endocrine prognostic factors, and to document the prevalence of thyroid hormone abnormalities.

RESULTS

Total triiodothyronine, and total and free thyroxine concentrations were decreased in 75.9, 34.7 and 4.5 per cent of cases, respectively. Dogs which were euthanased had significantly decreased total triiodothyronine, and total and free thyroxine concentrations compared with those which made a full recovery. Total triiodothyronine concentrations were significantly lower in dogs that were euthanased compared with those which made a partial recovery.

CLINICAL SIGNIFICANCE

Thyroid hormone concentrations may be used as prognostic indicators in dogs with non-thyroidal illness. Low triiodothyronine syndrome may be more common in dogs than previously recognised.

Non thyroidal illness: to treat or not to treat?

In critically ill patients, pronounced alterations in the hypothalamic-pituitary-thyroid axis occur without any evidence for thyroid disease. T3 decreases and rT3 increases within a few hours of the onset of disease. Severity and duration of disease are related to the magnitude of these changes. This manuscript discusses whether these changes in thyroid hormone levels during critical illness should be treated, and was in part published elsewhere.

Thyroid hormone transporters in health and disease: advances in thyroid hormone deiodination

Thyroid hormone metabolism by the three deiodinase selenoproteins -- DIO1, DIO2, and DIO3 -- regulates the local availability of various iodothyronine metabolites and thus mediates their effects on gene expression, thermoregulation, energy metabolism, and many key reactions during the development and maintenance of an adult organism. Circulating serum levels of thyroid hormone and thyroid-stimulating hormone, used as a combined indicator of thyroid hormone status, reflect a composite picture of: thyroid secretion; tissue-specific production of T(3) by DIO1 and DIO2 activity, which both contribute to circulating levels of T(3); and degradation of the prohormone T4, of the thyromimetically active T(3), of the inactive rT(3), of other iodothyronines metabolites with a lower iodine content and of thyroid hormone conjugates. Degradation reactions are catalyzed by either DIO1 or DIO3. Aberrant expression of individual deiodinases in disease, single nucleotide polymorphisms in their genes, and novel regulators of DIO gene expression (such as bile acids) provide a more complex picture of the fine tuning and the adaptation of systemic and local bioavailability of thyroid hormones.

Nutrition support and the chronic critical illness syndrome

Critical illness can be viewed as consisting of 4 distinct stages: (1) acute critical illness (ACI), (2) prolonged acute critical illness, (3) chronic critical illness, and (4) recovery. ACI represents the evolutionarily programmed response to a stressor. In ACI, substrate is shunted away from anabolism and toward vital organ support and inflammatory proteins. Nutrition support in this stage is unproven and may ultimately prove detrimental. As critical illness progresses, there is no evolutionary precedent, and man owes his life to modern critical care medicine. It is at this point that nutrition and metabolic support become integral to the care of the patient. This paper (1) delineates and develops the 4 stages of critical illness using current evidence, clinical experience, and new hypotheses; (2) defines the chronic critical illness syndrome (CCIS); and (3) details an approach to the metabolic and nutrition support of the chronically critically ill patient using the metabolic model of critical illness as a guide. It is our hope that this clinical model can generate testable hypotheses that can improve the outcome of this unique population of patients.

Deiodinases: implications of the local control of thyroid hormone action

The deiodinases activate or inactivate thyroid hormone, and their importance in thyroid hormone homeostasis has become increasingly clear with the availability of deiodinase-deficient animals. At the same time, heightened interest in the field has been generated following the discovery that the type 2 deiodinase can be an important component in both the Hedgehog signaling pathway and the G protein-coupled bile acid receptor 1-mediated (GPBAR1-mediated) signaling cascade. The discovery of these new roles for the deiodinases indicates that tissue-specific deiodination plays a much broader role than once thought, extending into the realms of developmental biology and metabolism.

Hypothalamic thyroid hormone feedback in health and disease

The role of the human hypothalamus in the neuroendocrine response to illness has only recently begun to be explored. Extensive changes in the hypothalamus-pituitary-thyroid (HPT) axis occur within the framework of critical illness. The best-documented change in the HPT axis is a decrease in serum concentrations of the biologically active thyroid hormone triiodothyronine (T3). From studies in post-mortem human hypothalamus it appeared that low serum T3 and thyrotropin (TSH) during illness (nonthyroidal illness, NTI) are paralleled by decreased thyrotropin-releasing hormone (TRH)mRNA expression in the hypothalamic paraventricular nucleus (PVN), pointing to a major alteration in HPT axis setpoint regulation. A strong decrease in TRHmRNA expression is also present in the PVN of patients with major depression as well as in glucocorticoid-treated patients. By inference, hypercortisolism in hospitalized patients with severe depression or in critical illness may induce down-regulation of the HPT axis at the level of the hypothalamus. In order to start defining the determinants and mechanisms of these setpoint changes in various clinical conditions, it is important to note that an increasing number of hypothalamic proteins appears to be involved in central thyroid hormone metabolism. In recent studies, we have investigated the distribution and expression of thyroid hormone receptor (TR) isoforms, type 2 and type 3 deiodinase (D2 and D3), and the thyroid hormone transporter monocarboxylate transporter 8 (MCT8) in the human hypothalamus by a combination of immunocytochemistry, mRNA in situ hybridization and enzyme activity assays. Both D2 and D3 enzyme activities are detectable in the mediobasal hypothalamus. D2 immunoreactivity is prominent in glial cells of the infundibular nucleus/median eminence region and in tanycytes lining the third ventricle. Combined D2, D3, MCT8 or TR immunocytochemistry and TRHmRNA in situ hybridization indicates that D3, MCT8 and TRs are all expressed by TRH neurons in the PVN, whereas D2 is not. Taken together, these results suggest that the prohormone thyroxine (T4) is taken up in glial cells that convert T4 into the biologically active T3 via the enzyme D2; T3 is subsequently transported to TRH producing neurons in the PVN where it may bind to TRs and/or may be degraded into inactive iodothyronines by D3. This model for thyroid hormone action in the human hypothalamus awaits confirmation in future experimental studies.