Relationship between thyrotropin and thyroxine changes during recovery from severe hypothyroxinemia of critical illness

Association of preoperative thyroid hormone replacement with perioperative complications after major abdominal surgery

OBJECTIVE

To determine the association between preoperative thyroid hormone replacement and complications following major abdominal surgery.

METHODS

A retrospective case series was performed of patients enrolled in the Michigan Surgical Quality Collaborative (MSQC) who underwent major abdominal surgery at an academic institution over a 10-year period. The principal explanatory variable was preoperative thyroid hormone replacement. Primary outcomes were morbidity, mortality and length of stay.

RESULTS

2700 patients were identified. On multivariate analysis correcting for established predictors of operative morbidity, patients on preoperative thyroid replacement had a 1.5- fold increased risk of serious morbidity(p ​= ​0.01), and a 1.7- fold greater risk for serious sepsis(p ​= ​0.04). Thyroid replacement was associated with longer length of stay(p ​< ​0.001). While there was a high degree of missing data for surgical approach (31.1 ​% missing data), results suggest that patients on thyroid hormone replacement were more likely to undergo an open rather than minimally invasive surgery(p ​< ​0.01). Open surgery was associated with greater risk of serious morbidity(p ​= ​0.003) and longer length of stay(p ​< ​0.001).

CONCLUSIONS

Preoperative thyroid hormone replacement independently predicts operative morbidity and length of stay following major abdominal surgery.

Total thyroxine, triiodothyronine, and thyrotropin concentrations during acute nonthyroidal illness and recovery in dogs

BACKGROUND

Acute illness can result in changes in serum total thyroxine (tT4), total triiodothyronine (tT3), and thyrotropin (TSH) concentrations in euthyroid dogs defined as nonthyroidal illness syndrome, but longitudinal evaluation of these hormones during the recovery phase is lacking.

OBJECTIVES

To longitudinally evaluate serum tT4, tT3, and TSH concentrations during the acute phase and recovery from acute illness in dogs.

ANIMALS

Nineteen euthyroid client-owned dogs hospitalized for acute illness at a veterinary teaching hospital.

METHODS

Prospective longitudinal study. Serum tT4, tT3, and TSH concentrations were measured at the admission (T0), at last day of hospitalization (T1), and during the recovery phase at 3, 7, 14, and 21 days after the discharge (T2, T3, T4, and T5), respectively.

RESULTS

tT4 and tT3 were below the reference interval (RI) at T0 in 3 (16%) and 18 (95%) dogs, respectively; tT4 normalized in all dogs early in the recovery phase, while low tT3 persisted at the end of the study in 16 (83%) dogs. Median TSH concentrations were increased at T5 compared with T1 (0.19 ng/mL [range 0.03-0.65] vs 0.11 ng/mL [range (0.05-0.26)], mean difference = 0.09 ng/mL; P = .03). Five (26%) dogs had TSH above the RI at least at 1 time point during the recovery phase. None of the dogs had concurrent low tT4 and high TSH during the study.

CONCLUSIONS AND CLINICAL RELEVANCE

In euthyroid dogs acute illness can interfere with evaluation of thyroid function up to 21 days during the recovery phase. Thyroid testing should be avoided or postponed in these dogs.

Approach to the Patient With Raised Thyroid Hormones and Nonsuppressed TSH

Measurement of free thyroid hormones (THs) and thyrotropin (TSH) using automated immunoassays is central to the diagnosis of thyroid dysfunction. Using illustrative cases, we describe a diagnostic approach to discordant thyroid function tests, focusing on entities causing elevated free thyroxine and/or free triiodothyronine measurements with nonsuppressed TSH levels. Different types of analytical interference (eg, abnormal thyroid hormone binding proteins, antibodies to iodothyronines or TSH, heterophile antibodies, biotin) or disorders (eg, resistance to thyroid hormone β or α, monocarboxylate transporter 8 or selenoprotein deficiency, TSH-secreting pituitary tumor) that can cause this biochemical pattern will be considered. We show that a structured approach, combining clinical assessment with additional laboratory investigations to exclude assay artifact, followed by genetic testing or specialized imaging, can establish a correct diagnosis, potentially preventing unnecessary investigation or inappropriate therapy.

Thyroid function tests during nonthyroidal illness syndrome and recovery in acutely ill dogs

BACKGROUND

Nonthyroidal illness syndrome (NTIS) can result in thyroid function test alterations that mimic hypothyroidism. The duration of NTIS-induced changes in dogs is not well-described.

OBJECTIVES

Document alterations in thyroid function tests during NTIS and recovery, and the time necessary for their resolution.

ANIMALS

From 103 dogs sampled, 25 euthyroid dogs with acute, resolvable illness having a low serum total thyroxine (TT4) concentration on admission were analyzed.

METHODS

Prospective observational study. Serum TT4 concentration was measured in 103 dogs within 4 hours of admission. If below the reference interval (RI), subsequent serum samples were obtained every 24 hours from admission until discharge (acute phase) and at 2 weeks and 4 weeks after discharge (recovery phase). Serum samples were submitted for batch measurement of serum TT4, free thyroxine (fT4), total 3,5,3'-triiodothyronine (TT3), and thyroid-stimulating hormone (TSH) concentrations.

RESULTS

In the cohort of dogs analyzed, serum TT4, TT3, and fT4 concentrations were below the RI in 100%, 80%, and 16% at admission; 20%, 80%, and 0% at discharge; 4%, 8%, and 0% at 2 weeks; and 0%, 0%, and 0% at 4 weeks, respectively. Serum TSH concentration was within the RI in 100% at admission and discharge, and above the RI in 4% and 12% at 2 weeks and 4 weeks, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

Naturally occurring NTIS in dogs induces alterations in thyroid function tests during acute illness and recovery. Measurement of serum TT4 concentration 2 to 4 weeks after discharge or serum fT4 concentration by ED during illness is recommended for accurate assessment of thyroid function in acutely ill dogs.

Effects of discontinuation of levothyroxine treatment in older adults: protocol for a self-controlled trial

BACKGROUND

Many older persons use the thyroid hormone levothyroxine which is often continued for life. Scientifically, there is much uncertainty whether simple continuation is the optimal approach. First, the physical need for levothyroxine can decrease with age thereby posing a higher risk of overtreatment and adverse effects. Second, large trials in subclinical hypothyroidism have shown no benefit for the use of levothyroxine. Interestingly, guidelines do not address re-evaluation of the indication. This self-controlled trial aims to determine the effects of discontinuation of levothyroxine treatment in older adults.

METHODS AND ANALYSIS

Participants are community-dwelling subjects aged ≥60 years using levothyroxine continuously at a stable dosage of ≤150 µg and a level of thyroid-stimulating hormone (TSH) <10 mU/L. After a control period of 12 weeks, levothyroxine treatment is discontinued gradually using a stepwise approach with regular monitoring of thyroid function guided by their GP. The primary outcome is the proportion of participants withdrawn from levothyroxine while maintaining a free T4 level within the reference range and a TSH level <10 mU/L, 52 weeks after the start of discontinuation. Secondary outcomes are compared with the control period (self-controlled) and include among others, the effects on thyroid-specific and general health-related quality of life. Furthermore, patients' attitudes towards deprescribing and regret regarding discontinuing levothyroxine treatment will be recorded. A total of 513 participants will be recruited to estimate the expected proportion of 50% with a 95% CI ranging from 45% to 55%.

ETHICS AND DISSEMINATION

Approval was obtained from the institutional Medical Ethics Committee. The Older People Advisory Board Health and Well-being has reviewed the research proposal and their comments were used for improvement. In line with the funding policies of the grant organisation funding this study, the study results will be proactively disseminated to the general public and key public health stakeholders.

TRIAL REGISTRATION NUMBER

NL7978; NCT05821881.

Study of Non-Thyroidal Illness Syndrome and Its Recovery in Critically Ill Patients at a Tertiary Care Centre in South India

Background and Objectives

Transient thyroid hormone alterations are common during critical illness and are termed non-thyroidal illness syndrome (NTIS). We studied the prevalence of NTIS in the ICU setting and its impact on predicting mortality and other outcomes and compared it to the Acute Physiology and Chronic Health Evaluation II (APACHE II) score.

Materials and Methods

The study included 119 consecutive patients admitted with a critical illness. APACHE II score was calculated. Total T3, total T4, TSH, free T3, and free T4 were measured at admission and after six weeks of discharge. NTIS and euthyroid groups were studied for ICU, hospital stays, mortality, readmission, and recovery. Predictors of mortality were compared between survivors and non-survivors.

Results

The mean age was 60.15 ± 14.50 years with M:F = 84 (71%):35 (29%). NTIS was observed in 84 (71%), low T3 being the most common abnormality in 53 (63%). The occurrence of NTIS was significantly higher among non-survivors (28/30, 93%) versus survivors (56/89, 63%) (P = 0.002). Non-survivors showed significantly lower T3, TSH, and FT3/FT4 ratios and higher readmissions. NTIS group showed significantly greater ICU stay (P = 0.02) and had higher readmission rates (P = 0.032). Baseline T3 had the greatest power to predict mortality. APACHE II score also correlated significantly with mortality (19.60 ± 10.58 vs 11.99 ± 6.80, P < 0.001). The area under the curve (0.677) for the T3 level was lower than the APACHE II score (0.760). After six weeks, 61% had recovered from NTIS.

Conclusions

NTIS was common amongst critically ill patients (71.5%), which reversed in 61% at six weeks. Low T3 was the most common abnormality and independently predicted mortality. Free T3/free T4 also significantly predicted mortality. The correlation between thyroid dysfunction and the severity of primary illness makes it an additional attractive low-cost marker of mortality.

Treating hypothyroidism is not always easy: When to treat subclinical hypothyroidism, TSH goals in the elderly, and alternatives to levothyroxine monotherapy

The majority of patients with hypothyroidism feel better when levothyroxine treatment restores thyroid-stimulating hormone (TSH) concentrations to normal. Increasingly, a significant minority of patients remain symptomatic and are dissatisfied with their treatment. Overzealous treatment of symptomatic patients with subclinical hypothyroidism may contribute to dissatisfaction among hypothyroidism patients, as potential hypothyroid symptoms in patients with minimal hypothyroidism rarely respond to treatment. Thyroid hormone prescriptions have increased by 30% in the United States in the last decade. The diagnosis of subclinical hypothyroidism should be confirmed by repeat thyroid function tests ideally obtained at least 2 months later, as 62% of elevated TSH levels may revert to normal spontaneously. Generally, treatment is not necessary unless the TSH exceeds 7.0-10 mIU/L. In double-blinded randomized controlled trials, treatment does not improve symptoms or cognitive function if the TSH is less than 10 mIU/L. While cardiovascular events may be reduced in patients under age 65 with subclinical hypothyroidism who are treated with levothyroxine, treatment may be harmful in elderly patients with subclinical hypothyroidism. TSH goals are age dependent, with a 97.5 percentile (upper limit of normal) of 3.6 mIU/L for patients under age 40, and 7.5 mIU/L for patients over age 80. In some hypothyroid patients who are dissatisfied with treatment, especially those with a polymorphism in type 2 deiodinase, combined treatment with levothyroxine and liothyronine may be preferred.

Thyroid Disfunction in Critically Ill COVID-19 Patients. Relationship with In-Hospital Mortality

The incidence of thyroid disfunction has not been analyzed in critically ill COVID-19 patients. Our objective was to analyze the relationship of the thyroid profile and in-hospital mortality in critically ill COVID-19 patients. This was a prospective single-center study involving critically ill COVID-19 patients admitted to the ICU of a tertiary University Hospital. Thyroid hormones were measured through drawing blood samples from a central venous catheter at ICU admission and on the fifth day. A multiple logistic regression analysis was performed to analyze the variables associated with mortality. The ability of the different thyroid hormones to predict in-hospital mortality was evaluated by calculating the receiver operating characteristics (ROCs) and the area under the curve (AUC). A total of 78 patients were included in the study at ICU admission; 72 had their thyroid profile measured at day 5. In-hospital mortality reached 29.5%. Multiple logistic regression analysis showed that variables associated with mortality were age and prior beta-blocker therapy at ICU admission and age fT4 at day 5. The AUC for in-hospital mortality predictions of fT4 at day 5 was 0.69. Thyroid responses are commonly observed in critically ill COVID-19 patients. fT4 at day 5 after ICU admission was associated with mortality.

Transient Hyperthyrotropinemia in Outpatient Children with Acute Infections of the Respiratory System

Background: Diagnostics of thyroid disorders (TD) are frequently based on the measurements of thyroid stimulating hormone (TSH) concentration only. If TSH is outside the reference range, the diagnostic procedure used in patients with TD isintroduced. Observations indicate that in a considerable number of these patients, TD is not confirmed. The aim of the study was to assess the incidence of transient hyperthyrotropinemia in healthy children during acute infections of the respiratory system. Patients and Methods: The study included consecutive children (49 boys and 45 girls), aged 2.2–17.3 years, who visited one General Practitioner (GP) due to respiratory tract infections. The tests: complete blood count (CBC), C-reactive protein (CRP), TSH and FT4 were run on the next day after the visit at the physician’s (initial visit) and ≥2 weeks after recovery. Results: Among these children, elevated TSH values were found in about 10% of patients, and they went back to normal values after recovery. A prospective analysis showed a reduction of TSH values in approx. 65% of all groups and TSH at the follow-up visit was significantly lower. Conclusions: Transient hyperthyrotropinemia was observed in about 10% of children with acute respiratory tract infection. This preliminary finding remains unexplained.

AAIT: A novel prognostic model for HIV-negative patients with cryptococcal meningoencephalitis New Scoring Model for Non-HIV Patients with CM

Cryptococcal meningitis (CM) is a common opportunistic infection in HIV-negative patients, with mortality rates as high as those in the HIV-negative population. This requires accurate initial clinical decision-making, warranting the development of a prognostic score. Two groups of patients were investigated separately to develop a novel prognostic model (AAIT) for HIV-negative patients with CM. A retrospective analysis of 201 HIV-negative patients with CM was conducted to develop the CM prognostic score. In addition, the CM cohort (n = 21) was recruited longitudinally to verify the new prognostic score. Meanwhile, the association between the prognostic score and 1-year mortality of CM was expounded. AAIT (age, albumin, combined bacterial infection, and total triiodothyronine) is a novel prognostic score based on age, albumin level, combined bacterial infection, and total triiodothyronine (TT3) level, which were significantly higher in nonsurvivors than in survivors (0.68 [-0.70 to 1.55] vs - 1.72 [-3.75 to -0.73], P < .00). Regarding the AAIT-predicted 1-year mortality, the area under the receiver operating characteristic curve (AUROC) value was 0.857, whereas it was 0.965 for the validation cohort. In the induction period, different treatment options did not seem to significantly improve the 1-year survival rate. AAIT is a straightforward and clear prognostic score that can add value to predict the outcomes in HIV-negative patients with CM. In addition, controlling infection and increasing the albumin and TT3 levels may help improve clinical outcomes in HIV-negative patients with CM.

LAY ABSTRACT

AAIT (age, albumin, combined bacterial infection, and total triiodothyronine) is a straightforward and clear prognostic score that can add value to predict the outcomes HIV-negative patients with CM.

Serum thyroxine and thyrotropin concentrations decrease with severity of nonthyroidal illness in cats and predict 30-day survival outcome

Background

In cats, nonthyroidal illness affects serum thyroid hormone concentrations. Serum thyroxine (T₄) and triiodothyronine (T₃) concentrations commonly decrease, whereas free T₄ (fT₄) concentrations vary unpredictably. Limited information exists regarding effects on serum thyrotropin (thyroid‐stimulating hormone [TSH]) concentrations in cats with nonthyroidal illness syndrome (NTIS).

Objectives

To characterize alterations in thyroid function that develop in cats with NTIS and to correlate these alterations with severity and outcome of the nonthyroidal illness.

Animals

Two hundred and twenty‐two cats with NTIS and 380 clinically normal cats of similar age and sex.

Methods

Prospective, cross‐sectional study. All cats had serum T₄, T₃, free T₄, and TSH concentrations measured. Cats were grouped based on illness severity and 30‐day survival.

Results

Cats with NTIS had lower serum T₄ and T₃ concentrations than did normal cats (P < .001). Serum fT₄ and TSH concentrations did not differ between groups. Serum T₄, T₃, and fT₄ concentrations progressively decreased with increasing disease severity (P < .001). The 56 cats that died had lower T₄, T₃, and TSH concentrations than did the 166 survivors, with no difference in fT₄ concentration. Multivariable logistic regression modeling indicated that serum T₄ and TSH concentrations both predicted survival (P < .02).

Conclusions and Clinical Importance

Cats with NTIS commonly develop low serum T₄, T₃, and TSH concentrations, the prevalence and extent of which increases with disease severity. Clinicians should consider evaluating thyroid function in cats with severe NTIS, because doing so could help determine probability of successful treatment responses before investing considerable time, effort, and finances in addressing the underlying disease.

Severe hyperthyroidism without symptoms due to nonthyroidal illness in a child with acute hepatitis: case report and literature review

While liver enzyme changes are frequently reported in hyperthyroidism, liver dysfunction itself can lead to alterations in thyroid hormone metabolism. However, the exact relationship between hyperthyroidism and liver dysfunction is unclear. We report an 11-year-old boy presenting with acute hepatitis of unknown etiology, who was incidentally found to have asymptomatic biochemical hyperthyroidism. Despite significant total and free T4 elevation, clinical evidence of thyrotoxicosis was absent. Thyroid I-123 uptake was also reduced. Additional testing revealed slight T3 elevation and significant rT3 elevation. Graves' and Hashimoto's thyroiditis testing was negative. We hypothesize that the biochemical hyperthyroidism was due to transient thyroiditis. Although an etiology for the boy's hepatitis was never determined, and an undiagnosed infectious etiology causing subacute thyroiditis was considered, subsequent testing showing positive thyroid peroxidase antibodies, suggesting autoimmune Hashimoto's thyroiditis as the likely cause of the hyperthyroidism. We believe, furthermore, that the absence of symptoms was the result of concurrent nonthyroidal illness resulting in the biochemical findings of slight T3 elevation and significant rT3 increase despite significant T4 elevation.

Hypothyroidism associated with therapy for multi-drug-resistant tuberculosis in Australia

BACKGROUND

Reports from resource-poor countries have associated thionamide- and para-aminosalicylate sodium (PAS)-based treatment of multi-drug-resistant tuberculosis (MDR-TB) with the development of hypothyroidism.

AIM

To identify predictors and assess the cumulative proportions of hypothyroidism in patients treated for MDR-TB with these agents in Australia.

METHODS

Retrospective multicentre study of MDR-TB patients from five academic centres covering tuberculosis (TB) services in Victoria, Australia. Patients were identified using each centre's pharmacy department and cross checked with the Victorian Tuberculosis Program. Hypothyroidism was categorised as subclinical if the thyroid-stimulating hormone was elevated and as overt if free thyroxine (fT4) was additionally reduced on two separate occasions. Our main outcome measured was the cumulative proportion of hypothyroidism (at 5 years from treatment initiation).

RESULTS

Of the 29 cases available for analysis, the cumulative proportion of hypothyroidism at 5 years was 37% (95% confidence interval (CI): 0-57.8%). Eight of the nine affected cases developed hypothyroidism within the first 12 months of treatment. Hypothyroidism was marginally (P = 0.06) associated with higher prothionamide/PAS dosing and was reversible with cessation of the anti-tuberculosis medication.

CONCLUSIONS

Prothionamide/PAS treatment-associated hypothyroidism is common in MDR-TB patients in Australia, emphasising the importance of regular thyroid function monitoring during this treatment. Thyroid hormone replacement, if initiated, may not need to be continued after MDR-TB treatment is completed.

Diagnosis and treatment of hypothyroidism in old people : A new old challenge

PURPOSE

To review the diagnosis and the treatment of both subclinical and overt hypothyroidism in old people, which could represent a challenge for the clinicians.

METHODS

Narrative literature review. An extensive literature search was performed using the databases of Scopus, Medline through PubMed, and Google Scholar from January 1975 to May 2019. The search terms were "hypothyroidism," "older adults," "elderly," and "myxedema."

RESULTS

Hypothyroidism is more common among older subjects in comparison to the younger counterparts. The hypothalamic-pituitary-thyroid axis and its hormones undergo significant changes due to the physiological aging process. For a correct diagnosis of hypothyroidism in old people clinicians must take such age-related changes into account.

CONCLUSIONS

The administration of replacement therapy in older adults should consider frailty, polypharmacy and a high risk to develop overtreatment symptoms. On the other hand, older patients with untreated or undertreated hypothyroidism may develop a state of myxedema coma.

Nonthyroidal Illness Syndrome Across the Ages

In conditions of acute illness, patients present with reduced plasma T3 concentrations without a concomitant rise in TSH. In contrast, plasma concentrations of the inactive hormone rT3 increase, whereas plasma concentrations of T4 remain low-normal. This constellation of changes, referred to as nonthyroidal illness syndrome (NTIS), is present across all ages, from preterm neonates and over-term critically ill infants and children to critically ill adults. Although the severity of illness strongly correlates with the severity of the NTIS phenotype, the causality of this association remains debated, and pathophysiological mechanisms remain incompletely understood. In the acute phase of illness, NTIS appears to be caused predominantly by an increased peripheral inactivation of thyroid hormones, in which reduced nutritional intake plays a role. Current evidence suggests that these acute peripheral changes are part of a beneficial adaptation of the body to reduce expenditure of energy and to activate the innate immune response, which is important for survival. In contrast, in more severely ill and prolonged critically ill patients, an additional central suppression of the thyroid hormone axis alters and further aggravates the NTIS phenotype. Recent studies suggest that this central suppression may not be adaptive. Whether treatment of this central component of NTIS in prolonged critically ill patients, with the use of hypothalamic releasing factors, improves outcome remains to be investigated in large randomized control trials.

Subclinical Hypothyroidism: A Review

IMPORTANCE

Subclinical hypothyroidism, defined as an elevated serum thyrotropin (often referred to as thyroid-stimulating hormone, or TSH) level with normal levels of free thyroxine (FT4) affects up to 10% of the adult population.

OBSERVATIONS

Subclinical hypothyroidism is most often caused by autoimmune (Hashimoto) thyroiditis. However, serum thyrotropin levels rise as people without thyroid disease age; serum thyrotropin concentrations may surpass the upper limit of the traditional reference range of 4 to 5 mU/L among elderly patients. This phenomenon has likely led to an overestimation of the true prevalence of subclinical hypothyroidism in persons older than 70 years. In patients who have circulating thyroid peroxidase antibodies, there is a greater risk of progression from subclinical to overt hypothyroidism. Subclinical hypothyroidism may be associated with an increased risk of heart failure, coronary artery disease events, and mortality from coronary heart disease. In addition, middle-aged patients with subclinical hypothyroidism may have cognitive impairment, nonspecific symptoms such as fatigue, and altered mood. In the absence of large randomized trials showing benefit from levothyroxine therapy, the rationale for treatment is based on the potential for decreasing the risk of adverse cardiovascular events and the possibility of preventing progression to overt hypothyroidism. However, levothyroxine therapy may be associated with iatrogenic thyrotoxicosis, especially in elderly patients, and there is no evidence that it is beneficial in persons aged 65 years or older.

CONCLUSIONS AND RELEVANCE

Subclinical hypothyroidism is common and most individuals can be observed without treatment. Treatment might be indicated for patients with subclinical hypothyroidism and serum thyrotropin levels of 10 mU/L or higher or for young and middle-aged individuals with subclinical hypothyroidism and symptoms consistent with mild hypothyroidism.

HINT: a novel prognostic model for patients with hepatitis B virus-related acute-on-chronic liver failure

BACKGROUND

HBV-related acute-on-chronic liver failure (HBV-ACLF) deteriorates rapidly in the short term, which necessitates accurate initial clinical decision making.

AIMS

To develop a novel prognostic score for patients with HBV-ACLF and clarify the role of thyroid hormones in HBV-ACLF.

METHODS

A retrospective cohort of 635 HBV-ACLF patients was enrolled to develop and validate a novel prognostic score for HBV-ACLF. Additionally, a cross-sectional cohort (n = 199) and a prospective longitudinal HBV-ACLF cohort (n = 56) were recruited to clarify the association between thyroid hormone status and the 30-day mortality of HBV-ACLF.

RESULTS

HINT, a novel prognostic score based on hepatic encephalopathy, INR, neutrophil count, and thyroid-stimulating hormone (TSH) using the deriving cohort (n = 426), was significantly higher in non-survivors than survivors (1.17 ± 2.38 vs -1.87 ± 1.26, P < 0.0001). The AUROC of HINT for 30-day mortality was 0.889, which was significantly higher than that of the Child-Pugh, MELD, CLIF-SOFA, CLIF-C ACLF, and COSSH-ACLF scores (all P < 0.05). These results were confirmed in the validation cohort (n = 209), except that the AUROC of HINT was comparable to that of COSSH-ACLF (P = 0.357). Among thyroid hormones, only the TSH level on admission was significantly lower in non-survivors than in survivors (P = 0.01). During the 14-day longitudinal observation, TSH levels increased significantly in the improvement group (P < 0.001) but did not change in the deterioration or fluctuation groups, and gradually increased in survivors (P < 0.001) but not in non-survivors.

CONCLUSIONS

HINT, as a prognostic score for HBV-ACLF, is simpler than and superior to the Child-Pugh, MELD, CLIF-SOFA, and CLIF-C ACLF scores and at least comparable with the COSSH-ACLF score. Sequential TSH measurements may facilitate prediction of the clinical course of ACLF.

Impact of Hypothyroidism and Heart Failure on Hospitalization Risk

BACKGROUND

Prior studies suggest that the relationship between hypothyroidism and mortality is dependent on underlying cardiovascular risk. Little is known about the association of hypothyroidism with hospitalization risk, and how these associations are modified by cardiovascular status.

METHODS

This study examined the association of thyroid status, defined by serum thyrotropin (TSH), with hospitalization risk among patients who received care at a large university-based tertiary care center between 1990 and 2015. Thyroid status was categorized as hypothyroidism versus euthyroidism (TSH >4.7 vs. 0.3-4.7 mIU/L, respectively). The relationship between thyroid status and hospitalization risk stratified by cardiovascular status was examined using multivariable Cox models.

RESULTS

Among 52,856 patients who met eligibility criteria, 49,791 (94.2%) had euthyroidism and 3065 (5.8%) had hypothyroidism. In analyses stratified by congestive heart failure (CHF) status, compared to euthyroidism, hypothyroidism was associated with higher risk of hospitalization in those with CHF but slightly lower risk in those without CHF (adjusted hazard ratio [aHRs] = 1.86 [confidence interval (CI) 1.17-2.94] and HR = 0.95 [CI 0.92-0.99], respectively; p = 0.006). In sensitivity analyses accounting for death as a competing event, underlying coronary artery disease modified the hypothyroidism-hospitalization relationship, such that stronger associations were observed among those with versus without coronary artery disease. In competing risk analyses, hypothyroidism was associated with higher versus lower risk of hospitalization among those with versus without cerebrovascular disease, respectively.

CONCLUSIONS

Hypothyroidism is associated with higher hospitalization risk among patients with underlying cardiovascular disease. Future studies are needed to determine whether correction of thyroid status with replacement therapy ameliorates hospitalization risk in this population.

Low triiodothyronine is associated with elevation of N-terminal pro-brain natriuretic peptide (NT-proBNP) and mortality in dialysis patients

BACKGROUND

Low thyroid hormone (TH) levels and myocardial damage are common in dialysis patients and are associated with mortality. However, little is known about the role of THs on myocardial damage as has been described in primary thyroid diseases. The aim of this study was to explore the potential relationship between low total triiodothyronine (total T3) and biomarkers of myocardial damage and the effect of their interaction on mortality, to ascertain if cardiovascular damage is the link between low THs and the risk of death in dialysis patients with CKD.

MATERIAL AND METHODS

TH plasma levels, nutritional markers, inflammation and myocardial damage were studied in 296 patients undergoing peritoneal dialysis or haemodialysis, who were followed up for 16 months to ascertain the association between biochemical variables and mortality.

RESULTS

Low total T3 levels were found in 45% of patients, which was inversely correlated with C-reactive protein (CRP) and NT-proBNP, and directly correlated with albumin and transferrin. Diabetes, CRP and total T3 were risk factors for all-cause mortality, and CRP, NT-proBNP and total T3 for cardiovascular mortality.

CONCLUSIONS

Low total T3 levels are common in dialysis patients and are associated with inflammation, malnutrition and myocardial damage. The latter may be the link between low THs and all-cause and cardiovascular mortality.

Hypothyroidism in Infants With Congenital Heart Disease Exposed to Excess Iodine

Thyroid hormone is critical for neonatal brain development, and even transient hypothyroidism can cause adverse neurocognitive outcomes. Infants exposed to excess iodine are at risk of developing hypothyroidism, especially those with congenital heart disease (CHD), because they are routinely exposed to excess iodine from intravenous iodinated contrast media and topical antiseptics. The aim of the present study was to identify the proportion of neonates with CHD exposed to iodine who developed hypothyroidism and to identify the associated risk factors. This was a retrospective study of neonates undergoing cardiac catheterization at Boston Children's Hospital during a 3-year period, some of whom also underwent cardiac surgery. Hypothyroidism was defined as an elevated thyroid-stimulating hormone level (>20 mIU/L at 24 to 96 hours of age and >15 mIU/L at >96 hours of age by heel-stick sampling and >9.1 mIU/L at 1 to 20 weeks of age by serum testing). Multivariate logistic regression was performed to predict the odds of developing hypothyroidism. Hypothyroidism was diagnosed incidentally in 46 of 183 infants (25%) with CHD after iodine exposure. Controlling for baseline cardiac risk, postnatal age, and gestational age, we found a fourfold increase in odds of developing hypothyroidism in neonates with serum creatinine >0.9 mg/dL and a fourfold increase in those who underwent more than three procedures. Hypothyroidism in neonates with CHD exposed to excess iodine is associated with multiple procedures and impaired renal function. Routine serial monitoring of thyroid function in these neonates is warranted. Future studies should examine the association between hypothyroidism and neurocognitive function in this population.

Changes in thyroid hormone concentrations during neonatal extracorporeal membrane oxygenation

OBJECTIVE

Thyroid hormone concentrations can be disturbed during critical illness. Our aim was to determine changes in thyroid hormone concentrations during neonatal extracorporeal membrane oxygenation (ECMO).

STUDY DESIGN

We included 21 ECMO-treated neonates. Age-specific s.d. scores (SDS) of free and total thyroxine (FT4; TT4), reverse and total triiodothyronine (rT3; TT3), thyroid-stimulating hormone (TSH) and thyroxine-binding globulin (TBG) were determined at six fixed time-points. Data were analyzed using general linear models.

RESULTS

At baseline, mean SDS FT4 (-0.78, 95% CI: -1.37 to -0.19), TT4 (-1.97, 95% CI: -2.76 to -1.18), TT3 (-0.88, 95% CI: -1.13 to -0.63), TSH (-2.14, 95% CI: -2.93 to -1.35) and TBG (-3.52, 95% CI: -4.55 to -2.50) were low with high mean SDS rT3 (0.53, 95% CI: 0.28 to 0.78). One hour after start ECMO, TT4, TSH and TBG had further declined; 12 h after start ECMO TT3 had declined (all P<0.05). After this decline, mean SDS TSH increased to the baseline level 12 h after start ECMO (-2.50, 95% CI: -3.22 to -1.79), and was higher than baseline 48 h after start ECMO (-0.56, 95% CI: -1.29 to 0.17). This TSH increase was followed by increases in TT4 and TT3. FT4 remained constant within the normal range during ECMO.

CONCLUSIONS

Thyroid hormone concentrations before ECMO were suggestive of non-thyroidal illness syndrome (NTIS). During ECMO, increases in TSH, TT4 and TT3 after an initial decline possibly reflect spontaneous restoration of the hypothalamic-pituitary-thyroid axis. FT4 remained constant within the normal range. This suggests that thyroxine therapy is not required during ECMO.

Euthyroid Sick Syndrome

In this review, we discuss the characteristics, pathophysiology, and therapeutic implications of the euthyroid sick syndrome. Multiple mechanisms have been identified to contribute to the development of euthyroid sick syndrome, including alterations in the iodothyronine deiodinases, thyroid-stimulating hormone secretion, thyroid hormone binding to plasma protein, transport of thyroid hormone in peripheral tissues, and thyroid hormone receptor activity. The euthyroid sick syndrome appears to be a complex mix of physiologic adaptation and pathologic response to acute illness. The underlying cause for these alterations has not yet been elucidated. Treatment of the euthyroid sick syndrome with thyroid hormone to restore normal serum thyroid hormone levels in an effort to improve disease prognosis and outcomes continues to be a focus of many clinical studies, although currently available data do not provide evidence of a clear benefit of treatment.

Thyroid hormone alterations in trauma patients requiring massive transfusion: An observational study

BACKGROUND

Although non-thyroidal illness syndrome (NTIS) is considered a negative prognostic factor, the alterations in free triiodothyronine (fT3) levels in trauma patients requiring massive transfusion have not been reported.

METHODS

A prospective observational study comparing 2 groups of trauma patients was conducted. Group M comprised trauma patients requiring massive transfusions (>10 units of packed red blood cells) within 24 hours of emergency admission. Group C comprised patients with an injury severity score >9 but not requiring massive transfusions. Levels of fT3, free thyroxine (fT4), and thyroid-stimulating hormone (TSH) were evaluated on admission and on days 1, 2, and 7 after admission. The clinical backgrounds and variables measured including total transfusion amounts were compared and the inter-group prognosis was evaluated. Results are presented as mean±standard deviation.

RESULTS

Nineteen patients were enrolled in each group. In both groups, 32 were men, and the mean age was 50±24 years. In group C one patient died from respiratory failure. The initial fT3 levels in group M (1.95±0.37 pg/mL) were significantly lower than those in group C (2.49±0.72 pg/mL; P<0.01) and remained low until 1 week after admission. Initial inter-group fT4 and TSH levels were not significantly different. TSH levels at 1 week (1.99±1.64 µIU/mL) were higher than at admission (1.48±0.5 µIU/mL) in group C (P<0.05).

CONCLUSION

Typical NTIS was observed in trauma patients requiring massive transfusions. When initial resuscitation achieved circulatory stabilization, prognosis was not strongly associated with NTIS.

Thyroid hormone replacement for nephrotic syndrome patients with euthyroid sick syndrome: a meta-analysis

OBJECTIVE

To assess the efficacy of thyroid hormone replacement therapy for nephrotic syndrome (NS) patients associated with euthyroid sick syndrome (ESS).

MATERIALS AND METHODS

The Cochrane library, ISI, Ovid, PubMed, Chinese Biomedicine Database were searched, and reference list of relevant articles were selected. Randomized controlled trials (RCTs) or quasi-RCTs with thyroid hormone replacement on NS patients associated with ESS were included in this analysis.

RESULTS

Six trials (329 participants) were included. Meta-analysis showed that thyroid hormone replacement therapy can significantly increase the completely remission rate [OR = 3.04, 95% confidence interval (CI): 3.04-1.88, p < 0.00001] and total response rate (OR = 4.63, 95% CI: 2.46-8.71, p < 0.00001) of NS patients associated with ESS. No side effect was observed during the follow-up period. There was no obvious publication bias in the mete-analysis studies.

CONCLUSIONS

Thyroid hormone replacement therapy significantly increases the remission of ESS in patients with NS.

The clinical use of thyroid function tests

Laboratory tests are essential for accurate diagnosis and cost-effective management of thyroid disorders. When the clinical suspicion is strong, hormonal levels just confirms the diagnosis. However, in most patients, symptoms are subtle and unspecific, so that only biochemical tests can detect the disorder. The objective of this article is to do a critical analysis of the appropriate use of the most important thyroid function tests, including serum concentrations of thyrotropin (TSH), thyroid hormones and antithyroid antibodies. Through a survey in the MedLine database, we discuss the major pitfalls and interferences related to daily use of these tests and recommendations are presented to optimize the use of these diagnostic tools in clinical practice.

Pitfalls in the measurement and interpretation of thyroid function tests

Thyroid function tests (TFTs) are amongst the most commonly requested laboratory investigations in both primary and secondary care. Fortunately, most TFTs are straightforward to interpret and confirm the clinical impression of euthyroidism, hypothyroidism or hyperthyroidism. However, in an important subgroup of patients the results of TFTs can seem confusing, either by virtue of being discordant with the clinical picture or because they appear incongruent with each other [e.g. raised thyroid hormones (TH), but with non-suppressed thyrotropin (TSH); raised TSH, but with normal TH]. In such cases, it is important first to revisit the clinical context, and to consider potential confounding factors, including alterations in normal physiology (e.g. pregnancy), intercurrent (non-thyroidal) illness, and medication usage (e.g. thyroxine, amiodarone, heparin). Once these have been excluded, laboratory artefacts in commonly used TSH or TH immunoassays should be screened for, thus avoiding unnecessary further investigation and/or treatment in cases where there is assay interference. In the remainder, consideration should be given to screening for rare genetic and acquired disorders of the hypothalamic-pituitary-thyroid (HPT) axis [e.g. resistance to thyroid hormone (RTH), thyrotropinoma (TSHoma)]. Here, we discuss the main pitfalls in the measurement and interpretation of TFTs, and propose a structured algorithm for the investigation and management of patients with anomalous/discordant TFTs.

A review of the evidence for and against increased mortality in hypothyroidism

The lifetime risk of overt hypothyroidism is around 5%, and this disease is usually preceded by subclinical hypothyroidism, which has an even higher prevalence (estimated to be up to 9%). Hypothyroidism has been linked with cardiac dysfunction, atherosclerosis, hypertension and coagulopathy. Intuitively, this increased morbidity is expected to shorten patients' lifespan, but definitive data are lacking on whether either of these hypothyroid states (particularly overt hypothyroidism) increase mortality. Study findings are inconsistent and, overall, the pooled data do not demonstrate increased mortality in patients with either subclinical or overt hypothyroidism. However, none of the available studies was adequately designed to answer this question. This Review discusses major shortcomings in those studies, such as population dissimilarities, hypothyroid state classification and misclassification, the inclusion of nonthyroidal illness, drug interference from concurrent therapies, serious comorbidities (for example, cardiovascular disease), differences in duration of follow-up and the number of levothyroxine-treated individuals. Taken together, the data exhibit little evidence of systematic bias and no strong scientific proof of increased mortality related to either subclinical or overt hypothyroidism. Future studies, however, should take the above-mentioned shortcomings and potential genetic confounding into consideration.

Low triiodothyronine syndrome: a prognostic marker for outcome in sepsis?

There is ongoing controversy as to whether hormonal changes of the euthyroid sick syndrome are predictors of poor outcome in sepsis and critical illness. In this prospective study, the prognostic accuracy of thyroid hormone levels in 103 critically ill adult patients on admission and during follow up in a medical intensive care unit (ICU) was assessed and was compared to clinical risk scores, namely, the acute physiology and chronic health evaluation and the simplified acute physiology score. Median T3 levels on admission to the ICU were lower in the 53 septic cases [0.9 nmol/l (IQR 0.6-1.1)] as compared with the 50 patients with a systemic inflammatory response syndrome [1.2 nmol/l (IQR 0.8-1.4), P < 0.001]. The lowest T3 levels were found in patients with severe sepsis [0.8 nmol/l (IQR 0.55-0.95)] and septic shock [0.8 nmol/l (IQR 0.6-1.0)]. There was no difference in T3 and free thyroxin (fT4) levels on admission in non-survivors compared with survivors overall and in subgroups of patients with SIRS and sepsis. During the follow up, fT4 levels decreased significantly in non-survivors, while they increased in survivors [fT4 difference -1.3 (IQR -2.5 to 0.2) vs. 0.8 (IQR -0.85 to 4.1), P = 0.003]. In addition, on the day of death, non-survivors had lower T3 and fT4 levels as compared with survivors (P = 0.04 and P = 0.02). T3 and fT4 levels on admission were not prognostic in this cohort of critically ill patients. A decrease in fT4 levels in the course of disease, however, may point to adverse outcome.

The clinical significance of subclinical thyroid dysfunction

Subclinical thyroid disease (SCTD) is defined as serum free T(4) and free T(3) levels within their respective reference ranges in the presence of abnormal serum TSH levels. SCTD is being diagnosed more frequently in clinical practice in young and middle-aged people as well as in the elderly. However, the clinical significance of subclinical thyroid dysfunction is much debated. Subclinical hyper- and hypothyroidism can have repercussions on the cardiovascular system and bone, as well as on other organs and systems. However, the treatment and management of SCTD and population screening are controversial despite the potential risk of progression to overt disease, and there is no consensus on the thyroid hormone and thyrotropin cutoff values at which treatment should be contemplated. Opinions differ regarding tissue effects, symptoms, signs, and cardiovascular risk. Here, we critically review the data on the prevalence and progression of SCTD, its tissue effects, and its prognostic implications. We also examine the mechanisms underlying tissue alterations in SCTD and the effects of replacement therapy on progression and tissue parameters. Lastly, we address the issue of the need to treat slight thyroid hormone deficiency or excess in relation to the patient's age.

Endocrine assessments during critical illness

The evaluation of hormonal status in critically ill patients is challenging and has many pitfalls. This article reviews proper assessment of glycemic status AND adrenal and thyroid function during critical care.

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.

Transient hypothyroxinaemia in preterm infants

Thyroid hormones are required for normal development of the brain. Transient hypothyroxinaemia is the most common thyroid dysfunction in preterm infants and is defined by temporary low levels of T4, T3 and normal or low TSH. Low T4 levels in preterm infants are associated with persistent neurodevelopmental deficits in cognitive and motor function. Thyroid hormone substitution trials to date are underpowered and show inconsistent results; the question remains -- are low T4 levels simply an epiphenomenon? The aetiology of transient hypothyroxinaemia is multifactorial and the components amenable to correction form the basis of the therapeutic strategy: rectification of iodine deficiency in parenteral nutrition; a reduction of non-thyroidal illnesses and attenuation of their severity; and substitution of drugs that interfere with the hypothalamic-pituitary-thyroid axis. Thyroxine substitution therapy should only be done in the context of clinical trials and only in those infants who are hypothyroxinaemic.

Changes within the thyroid axis during the course of critical illness

This article reviews the mechanisms behind the observed changes in plasma thyroid hormone levels in the acute phase and the prolonged phase of critical illness. It focuses on the neuroendocrinology of the low triiodothyronine syndrome and on thyroid hormone metabolism by deiodination and transport.

Changes within the thyroid axis during critical illness

Pronounced alterations in plasma thyroid stimulating hormone and thyroid hormone levels occur during critical illness without any evidence for thyroid disease. Plasma T3 decreases and plasma rT3 increases within a few hours after the onset of disease, and the magnitude of these changes is related to the severity and the duration of the disease. This article reviews the mechanisms behind the observed changes, and focuses on the regulation of thyroid hormone deiodination and transport, as well as the potential positive or negative effects for both the acute and the chronic phase of critical illness.

Tissue thyroid hormone levels in critical illness

CONTEXT

Pronounced alterations in serum thyroid hormone levels occur during critical illness. T3 decreases and rT3 increases, the magnitudes of which are related to the severity of disease. It is unclear whether these changes are associated with decreased tissue T3 concentrations and, thus, reduced thyroid hormone bioactivity. PATIENTS AND STUDY QUESTIONS: We therefore investigated, in 79 patients who died after intensive care and who did or did not receive thyroid hormone treatment, whether total serum thyroid hormone levels correspond to tissue levels in liver and muscle. Furthermore, we investigated the relationship between tissue thyroid hormone levels, deiodinase activities, and monocarboxylate transporter 8 expression.

RESULTS

Tissue iodothyronine levels were positively correlated with serum levels, indicating that the decrease in serum T3 during illness is associated with decreased levels of tissue T3. Higher serum T3 levels in patients who received thyroid hormone treatment were accompanied by higher levels of liver and muscle T3, with evidence for tissue-specific regulation. Tissue rT3 and the T3/rT3 ratio were correlated with tissue deiodinase activities. Monocarboxylate transporter 8 expression was not related to the ratio of the serum over tissue concentration of the different iodothyronines.

CONCLUSION

Our results suggest that, in addition to changes in the hypothalamus-pituitary-thyroid axis, tissue-specific mechanisms are involved in the reduced supply of bioactive thyroid hormone in critical illness.

Hypothyroidism

Hypothyroidism is common, potentially serious, often clinically overlooked, readily diagnosed by laboratory testing, and eminently treatable. The condition is particularly prevalent in older women, in whom autoimmune thyroiditis is common. Other important causes include congenital thyroid disorders, previous thyroid surgery and irradiation, drugs such as lithium carbonate and amiodarone, and pituitary and hypothalamic disorders. Worldwide, dietary iodine deficiency remains an important cause. Hypothyroidism can present with nonspecific constitutional and neuropsychiatric complaints, or with hypercholesterolaemia, hyponatraemia, hyperprolactinaemia, or hyperhomocysteinaemia. Severe untreated hypothyroidism can lead to heart failure, psychosis, and coma. Although these manifestations are neither specific nor sensitive, the diagnosis is confirmed or excluded by measurements of serum thyrotropin and free thyroxine. Thyroxine replacement therapy is highly effective and safe, but suboptimal dosing is common in clinical practice. Patient noncompliance, drug interactions, and pregnancy can lead to inadequate treatment. Iatrogenic thyrotoxicosis can cause symptoms, and, even when mild, provoke atrial fibrillation and osteoporosis. We summarise present understanding of the history, epidemiology, pathophysiology, and clinical diagnosis and management of hypothyroidism.

5: Diagnosis and management of hyperthyroidism and hypothyroidism

The most common cause of hyperthyroidism in Australia is Graves disease, caused by a defect in immunoregulation in genetically predisposed individuals, leading to production of thyroid-stimulating antibodies. Each of the three modalities of therapy for Graves disease--thionamide drugs, subtotal or total thyroidectomy, and radioactive iodine ablation--can render the patient euthyroid, but all have potential adverse effects and may not eliminate recurrences. Hypothyroidism occurs in about 5% of the adult population; most present with "subclinical" hypothyroidism (mild thyroid failure), characterised by raised levels of serum thyroid stimulating hormone (TSH) but normal free thyroxine (T(4)). The most common cause of hypothyroidism in Australia is autoimmune chronic lymphocytic thyroiditis, characterised by raised circulating levels of thyroid peroxidase antibody. Symptoms and signs of hypothyroidism are often mild or subtle and, when there is clinical suspicion, thyroid function tests are needed; if serum TSH level is raised, free T(4) and thyroid peroxidase antibody should be measured. Replacement therapy with thyroxine is the cornerstone of therapy (1.6 microg/kg lean body weight daily, taken on an empty stomach); combination therapy with thyroxine and liothyronine (T(3)) is promoted, but there is little evidence of its clinical benefit. Despite the development of highly sensitive laboratory tests, clinical assessment and judgement remain paramount

Critical issues in endocrinology

Endocrine emergencies are commonly encountered in the ICU. This article focuses on several important endocrine emergencies, including diabetic hyperglycemic states, adrenal insufficiency, myxedema coma, thyroid storm, and pituitary apoplexy. Other endocrine issues that are related to intensive care, such as intensive insulin therapy, relative adrenal insufficiency, and thyroid function test abnormalities are also covered in detail.

L-thyroxine therapy attenuates the decline in serum triiodothyronine in nonthyroidal illness induced by hysterectomy

It is controversial whether the administration of thyroid hormone to patients with nonthyroidal illness has any beneficial effect. Two groups of patients undergoing abdominal hysterectomy under the same general anesthesia were studied. Group A consisted of 15 women taking chronically l-thyroxine therapy (1.8 mug/kg daily), and group B (control) consisted of 16 apparently healthy euthyroid women taking placebo. Thyroid hormones, cortisol, and interleukin (IL)-6 were measured 1 day before and 1, 2, 3, and 6 days after surgery. Total triiodothyronine (TT(3)) decreased to a significantly greater degree (P <.05) and for a longer period of time in group B than in group A. The significant increase of reverse T(3) (rT(3)) noted early in group B failed to reach the baseline levels until the end of the study, whereas in group A, rT(3) returned to the preoperative values by day 2. Both groups had similar free thyroxine (FT(4)) at baseline. FT(4) increased significantly at day 1 and remained significantly elevated throughout the postoperative period in group B only. Serum TT(4), thyroid-stimulating hormone (TSH), and cortisol did not change significantly in either group. In all patients, IL-6 increased significantly to a peak value at day 1, showing a slow decrease thereafter. A stronger negative correlation was found between T(3) and IL-6 in group B than in group A (r = -.66, P <.0001 v r = -.38, P <.001, respectively) and a strong positive correlation was observed between rT(3) and IL-6 in group B only (r =.57, P <.001). The long-term treatment with T(4) seems to attenuate the decrease of serum T(3), which occurs during the development of nonthyroidal illness postoperatively. The elevation of IL-6 accounted for a greater proportion of the variations of the T(3) and rT(3) in the control group B than in the T(4)-treated group A.

Heart failure accompanied by sick euthyroid syndrome and exercise training

Sick euthyroid syndrome is defined as the decrease of serum free triiodothyronine with normal free L-thyroxin and thyrotropin. Its appearance in patients with chronic heart failure is an indicator of severity. Exercise training through a wide variety of mechanisms reverses sick euthyroid syndrome (normalization of free triiodothyronine levels) and improves the ability to exercise. There is a connection during exercise among dyspnea, hyperventilation, fatigue, catecholamines, a decrease in the number and function of beta-blocker receptors, and elevation of serum free triiodothyronine. It is not known whether sick euthyroid syndrome contributes to the development of heart failure or is only an attendant syndrome.

Case finding and screening strategies for thyroid dysfunction

BACKGROUND

A case can be made for routine testing for thyroid dysfunction (TD) in women aged over 50 years once every 5 years when they present for medical care (case finding). This recommendation is based on: (i) the prevalence of TD, predominantly hypothyroidism, (ii) the insensitivity of standard clinical assessment in detecting even overt TD, (iii) the sensitivity of a single test, serum thyroid stimulating hormone (TSH), in identifying both over- and under-function, (iv) the probable adverse consequences of failure to recognize even mild TD, (v) the safety and effectiveness of treatment, and (vi) presumed lack of adverse effect from the testing program.

METHODS

A normal serum TSH value has a high negative predictive value in ruling out primary TD; if TSH is abnormal, measurement of serum free thyroxine (T(4)) and further clinical assessment are both required to establish the degree of TD.

RESULTS

Case finding identifies more "subclinical" or mild TD (abnormal TSH, normal T(4) and triiodothyronine (T(3))), than overt disease, but a major benefit of widespread testing is the earlier detection and treatment of unsuspected overt disease. There is now evidence that mild TD has adverse consequences and should not merely be regarded as a prognostic indicator, but there is still no consensus whether there is a causal relationship between mild thyroid failure and dyslipidemia.

CONCLUSIONS

A case can be made for treatment of both mild thyrotoxicosis and hypothyroidism, but the therapeutic decision is generally simpler for hypothyroidism.

Thyroid function in neonates with severe respiratory failure on extracorporeal membrane oxygenation

The object was to study thyroid function in neonates with severe respiratory failure on extracorporeal membrane oxygenation (ECMO) and determine whether abnormal thyroid function correlates with prognosis. Total and free thyroxine (T4, FT4), total and free triiodothyronine (T3, FT3), reverse triiodothyronine (rT3), thyroid-stimulating hormone, and thyroxine binding globulin were measured in 14 newborn infants with severe respiratory failure (age 1-30 days) from samples collected before anesthesia for cannula placement, at 30, 60, and 360 min after initiation of ECMO, and on days 2, 4, 6, and 8. The patients were divided into survivors and non-survivors for statistical analyses. No differences were noted between survivors and non-survivors in the pre-ECMO mean serum concentrations of the thyroid function tests analyzed. In nine survivors, mean serum T4, FT4, T3, FT3, and rT3 all declined significantly within 30-60 min after initiation of ECMO, compared to baseline values. The values for all mean serum concentrations recovered completely and exceeded baseline between days 2 and 8. In five non-survivors, the decline of all mean serum values was not statistically significant and recovery to baseline was not achieved. The ratios of mean serum concentration of rT3/FT3 were significantly different between survivors and non-survivors across all times during the ECMO course (p < 0.0005). These findings indicate that abnormalities in thyroid function occur in neonates with severe respiratory failure on ECMO and that the rT3/FT3 ratio correlates with prognosis over the ECMO course. Survival was associated with a significant reduction of serum thyroid hormone concentrations followed by recovery. We speculate that, in neonates with respiratory failure on ECMO, adaptive mechanisms which enhance survival include the capacity to down-regulate the pituitary-thyroid axis.

Serum thyroid-stimulating hormone measurement for assessment of thyroid function and disease

Third generation thyroid stimulating hormone (TSH) assays have emerged as the single most useful test of thyroid function, and are used widely and appropriately as a screening test. TSH measurement alone may be misleading in complicated patients and those undergoing treatment for thyroid dysfunction. Before obtaining thyroid function tests, clinicians need to consider whether the patient might have pituitary or hypothalamic disease or severe nonthyroidal illness, and whether assessment of the pituitary-thyroid axis reflects steady-state conditions. Subclinical hyperthyroidism is associated with adverse effects on the skeleton and the heart, and is best assessed by measurement of serum TsH with a third-generation assay.

Leptin and leptin receptor in anterior pituitary function

Leptin is a 16 kDa protein that exerts important effects on the regulation of food intake and energy expenditure by interacting with the leptin receptor in the brain and in many other tissues. Although leptin is produced mainly by white adipose tissue, several laboratories have shown low levels of leptin production by a growing number of tissues including the anterior pituitary gland. Many studies have implicated leptin in anterior pituitary function including the observation that homozygous mutations of the leptin receptor gene led to morbid obesity, lack of pubertal development and decreased GH and TSH secretion. In addition, leptin functions as a neuroendocrine hormone and regulates many metabolic activities. Leptin also interacts with and regulates the hypothalamic-pituitary-adrenal, the hypothalamic-pituitary-thyroid and the hypothalamic-pituitary-gonadal axes. All of the anterior pituitary cell types express the leptin receptor. However, leptin has been localized in specific subtypes of anterior pituitary cells indicating cell type-specific production of leptin in the anterior pituitary. Subcellular localization of leptin indicates co-storage with secretory granules and implicates hypothalamic releasing hormones in leptin secretion from anterior pituitary hormone cells. Leptin signal transduction in the anterior pituitary has been shown to involve the janus protein-tyrosine kinase (JAK)/signal transducer and activation of transcription (STAT) as well as suppressor of cytokine signalling (SOCS). These proteins are activated by tyrosine-phosphorylation in anterior pituitary cells. The various steps in pituitary leptin signal transduction remain to be elucidated.

Hypothyroidism: its incidence and prevalence in adults older than 55 years of age in an acute rehabilitation unit

OBJECTIVE

To investigate the incidence and prevalence of hypothyroidism in the acute rehabilitation unit.

DESIGN

Retrospective chart review.

SETTING

Inpatient rehabilitation unit.

PATIENTS

Thirty-five men and 91 women older than the age of 55 years (average, 74 years) separated into postsurgical (PS) and nonsurgical (NS) groups. Twenty-two men and 76 women were PS, 21 of whom had a history of hypothyroidism. Thirteen men and 15 women were NS, and 4 in this group had a history of hypothyroidism.

MAIN OUTCOME MEASURES

Levels of thyroid-stimulating hormone and free thyroxine.

RESULTS

There were 34 cases of hypothyroidism, a prevalence rate of 27%. The incidence of newly diagnosed cases was 9% (9 of 101). Six of the newly diagnosed cases were PS patients and three were NS patients. Eleven cases of undertreated hypothyroidism were found, in 9 PS patients and 2 NS patients. The rate of undertreated hypothyroidism in the PS population was 43% (9 of 21); in the nonsurgical population, it was 50% (2 of 4). The overall rate of undertreated hypothyroidism for both PS and NS groups was 44% (11 of 25).

CONCLUSION

There is a high prevalence of hypothyroidism on an inpatient rehabilitation unit and a high rate of undertreated hypothyroidism in PS patients. Screening high-risk patients is recommended.