Interactions between thyroid and kidney function in pathological conditions of these organ systems: a review

A comprehensive analysis of albuminuria in canine chronic kidney disease

BACKGROUND

Albuminuria, an important marker of decreased kidney function in chronic kidney disease (CKD), is not routinely used for CKD detection or proteinuria appearance. Its relationships with biochemical parameters and blood pressure in dogs are poorly understood.

OBJECTIVES

This study aimed to evaluate the relationship of albuminuria with various CKD markers, its correlation with the urinary protein to creatinine ratio (UPC), and hypertension in dogs with early stages of CKD. It also sought to determine the usability of the urinary albumin to creatinine ratio (UAC) for CKD screening.

METHODS

The study reviewed records of 102 dogs, categorising them into four groups based on disease status. UAC and UPC ratio, biochemistry and haematology variables, age, and systolic blood pressure were determined.

RESULTS

The Pearson's correlation coefficient between log-transformed values of UPC and UAC was r = 0.902 (95% CI: 0.87 to 0.93). Median UAC ratio values were 2.1 mg/g for the Healthy control group (n = 17), 54.2 mg/g for early stages CKD (n = 42), 5.8 mg/g for Acute sick control (n = 30), and 104 mg/g for Chronic sick control (n = 13). Thresholding UAC ratio as an indicator for impaired kidney function with the threshold of 10 mg/g (established based on the receiver operating characteristic curve) had a sensitivity 81.8%, specificity of 89.4%, positive predictive value (PPV) 90%, and negative predictive value (NPV) 80.1%. The correlation of UAC with biochemistry and haematology variables was statistically significant; for SDMA (μg/L), it was r = 0.566 and for other variables, it was weak to moderate. UAC was markedly elevated in cases of severe hypertension.

CONCLUSIONS

UAC ratio was significantly different among dogs with impaired and not impaired kidney function. The correlation strength for the UAC and UPC ratios was high. UAC ratio may be a promising marker for proteinuria analysis in dogs with CKD or other kidney function alterations.

Renal dysfunction caused by severe hypothyroidism diagnosed by renal biopsy: a case report

There is a close relationship between thyroid dysfunction and renal dysfunction. However, thyroid dysfunction can unfortunately result in inaccurate measurements of serum creatinine and cystatin C levels. The chronic decrease in cardiac output due to hypothyroidism can reduce renal plasma flow (RPF) resulting in renal dysfunction. We report the case of a 36-year-old male in whom renal dysfunction detected during a company health check-up was found to be caused by severe hypothyroidism. His serum creatinine levels showed poor results, but serum cystatin C levels were within the normal range. The physician thus prioritized serum cystatin C for assessing the patient's renal function, and concluded that his renal function was normal. He subsequently visited our hospital, aged 36 years, for a comprehensive examination. His serum creatinine level was 1.88 mg/dL and his serum cystatin C level was 0.75 mg/dL, indicating an unusual discrepancy between the two measurements. The patient also presented with fatigue, suggesting hypothyroidism, and we therefore evaluated his thyroid function. His free thyroxine level was below the sensitivity of the assay, while his thyroid-stimulating hormone level was > 100 μIU/mL. A renal biopsy was performed to further explore the underlying cause of his renal dysfunction, which suggested that reduced RPF could be the leading cause of his renal ischemia, with no indications of chronic glomerulonephritis or other abnormalities. His hypothyroidism and renal function improved after thyroid hormone replacement therapy. Given the limited reports of renal biopsy tissue examination during the acute phase of hypothyroidism, the current case provides important information regarding the diagnosis of renal dysfunction in patients with hypothyroidism.

Thyroid function and thyroid homeostasis parameters are associated with increased urinary albumin excretion in euthyroid individuals over 60 years old from NHANES

Introduction

The relationship between thyroid function/homeostasis parameters and renal function has been extensively studied. However, the relationship between thyroid function and thyroid homeostasis parameters with albuminuria among elderly individuals remains unclear.

Methods

The population was divided into an albuminuria group and a non-albuminuria group for baseline characteristic difference analysis. Multivariable logistic regression was used to test the association between thyroid function, and thyroid homeostasis parameters and albuminuria. The nonlinear relationship was explored with restricted cubic splines. Meanwhile, we investigated whether the relationship also existed in the diabetes and hypertension subgroups. Receiver operating characteristic (ROC) curves were used to assess the effectiveness of the indices.

Results

FT4 and TFQIFT4 were positively correlated with albuminuria (OR = 1.12; 95% CI = 1.02-1.23, p = 0.02; OR = 1.79; 95% CI = 1.08-2.99, p = 0.03), and FT3/FT4 was negatively correlated with albuminuria (OR = 0.03; 95% CI = 0.00-0.26, p = 0.003). Additionally, the nonlinear relationship between FT3/FT4 as well as TSHI and albuminuria was approximately U-shaped. Similar results were observed in the hypertension subgroup but not in the diabetes subgroup. There was a U-shaped nonlinear relationship between FT3 and albuminuria in the diabetes group. In addition, FT3/FT4 performed better than TFQI, TT4RI, and TSHI in ROC analyses for albuminuria prediction.

Conclusion

FT4, TFQIFT4, and a low FT3/FT4 ratio were risk factors for albuminuria in euthyroid individuals over 60 years old. However, FT3 was more associated with albuminuria in the diabetes subgroup. TSH was not associated with albuminuria in any analysis. In our study, we attempted to provide more reasonable thyroid parameters and basis for evaluating patients with underlying albuminuria. FT3/FT4 may be used as a helpful indicator to predict albuminuria and provide novel ideas for the evaluation and treatment of albuminuria.

Urine concentrating ability in cats with hyperthyroidism: Influence of radioiodine treatment, masked azotemia, and iatrogenic hypothyroidism

BACKGROUND

Hyperthyroid cats often have urine specific gravity (USG) values <1.035. It remains unclear how USG changes after treatment, if USG can be used to predict azotemia after treatment, or how iatrogenic hypothyroidism influences USG values.

OBJECTIVES

To determine the proportion of hyperthyroid cats with USG <1.035 vs ≥1.035; if USG changes after treatment; and whether USG <1.035 correlated with unmasking of azotemia or hypothyroidism.

ANIMALS

Six hundred fifty-five hyperthyroid cats treated with radioiodine; 190 clinically normal cats.

METHODS

Prospective, before-and-after study. Hyperthyroid cats had serum thyroxine, thyroid-stimulating hormone, and creatinine concentrations, and USG measured before and 6 months after successful treatment with radioiodine.

RESULTS

Of untreated hyperthyroid cats, USG was ≥1.035 in 346 (52.8%) and <1.035 in 309 (47.2%). After treatment, 279/346 (80.6%) maintained USG ≥1.035, whereas 67/346 (19.4%) became <1.035; 272/309 (88%) maintained USG <1.035, whereas 37/309 (12%) became ≥1.035. Only 22/346 (6.4%) with USG ≥1.035 developed azotemia after treatment, compared with 136/309 (44%) with <1.035 (P < .001). Of cats remaining nonazotemic, 38% had USG <1.035, compared with 20% of normal cats (P < .001). The 137 cats with iatrogenic hypothyroidism had lower USG after treatment than did 508 euthyroid cats (1.024 vs 1.035), but USGs did not change after levothyroxine supplementation. USG <1.035 had high sensitivity (86.1%) but moderate specificity (65.2%) in predicting azotemia after treatment.

CONCLUSIONS AND CLINICAL IMPORTANCE

Hyperthyroidism appears not to affect USG in cats. However, cats with evidence of sub-optimal concentrating ability before radioiodine treatment (USG < 1.035) are more likely to develop azotemia and unmask previously occult chronic kidney disease. Iatrogenic hypothyroidism itself did not appear to affect USG values.

The Prevalence of Thyroid Abnormalities in Patients With Chronic Kidney Disease: A Cross-Sectional Study at a Tertiary Care Hospital

Background and objective Chronic kidney disease (CKD) is a clinical syndrome characterized by the irreversible loss of kidney function. It is a widespread condition affecting populations worldwide. The kidneys play a crucial role in the metabolism, breakdown, and elimination of thyroid hormone and thyroid-stimulating hormone (TSH). Consequently, thyroid dysfunction can occur as an endocrine manifestation in CKD patients. Previous studies investigating thyroid abnormalities and the severity of CKD have yielded diverse outcomes. In light of this, this study aimed to determine the prevalence of thyroid dysfunction in CKD patients and explore the association between different thyroid dysfunctions and markers of kidney function. Methods A total of 140 CKD patients who met the inclusion criteria were recruited, and their demographic details and routine investigations were recorded. Blood samples were collected for kidney function tests and thyroid function tests. The primary outcome measures included markers of kidney function [urea, creatinine, and estimated glomerular filtration rate (e-GFR)] and thyroid profile [TSH, free thyroxine (FT4), and free triiodothyronine (FT3)]. Mean and standard deviation (SD) were calculated for continuous variables, while frequencies were calculated for categorical data. Fisher's exact test was employed to evaluate the association between two categorical variables, and p-values below 0.05 were considered statistically significant. Results The mean (± SD) urea, creatinine, and e-GFR were found to be 139 (± 81.1) mg/dL, 5.33 (± 4.1) mg/dL, and 20.1 (± 15) ml/min/1.73 m2, respectively. Of note, 133 (95%) patients had elevated urea levels, with the majority (n = 109, 77.8%) having urea levels between 40 and 199 mg/dL; 70 (50%) patients had creatinine levels less than 4 mg/dL, and 107 (76.4%) had e-GFR of less than 30 ml/min/1.73 m2. The mean (± SD) TSH, FT4, and FT3 levels were found to be 6.64 (± 11.2) mIU/ml, 13.6 (± 4.54) pmol/L, and 2.65 (± 1.89) pmol/L, respectively. It was observed that 18 (12.9%, 95% CI: 8.29-19.4%) of the CKD patients had hypothyroidism and 21 (15%, 95% CI: 10.02-21.8%) had subclinical hypothyroidism (SCH), while only two (1.4%, 95% CI: 0.39-5.05%) and five (3.6%, 95% CI: 1.5-8.08%) had hyperthyroidism and subclinical hyperthyroidism, respectively. Thirty-nine (27.9%, 95% CI: 21.1-35.8%) patients had low FT4 levels, whereas a considerable majority (n = 123, 87.9%, 95% CI: 81.41-92.28%) of the patients suffering from CKD were found to have low FT3 levels. The associations of urea levels with SCH, low FT4, and FT3 status were found to be statistically significant with p-values of 0.002, 0.033, and <0.001, respectively. The association between e-GFR and low FT3 status was also statistically significant, with a p-value of 0.014. Conclusion Nine out of 10 patients with CKD were discovered to have low FT3 levels, whereas one in four patients had low FT4 levels. The study participants also exhibited a significant presence of SCH and hypothyroidism, with prevalence rates of 15% and 12.9%, respectively. Urea levels and e-GFR, indicating the severity of CKD, showed a significant association with the presence of various thyroid abnormalities. Hypothyroidism in CKD patients can complicate disease progression, impact mortality rates, and affect overall quality of life. Therefore, routine screening for thyroid abnormalities should be conducted in all CKD patients.

Thyroid Dysfunction at Different Stages of Chronic Kidney Disease: A Cross-Sectional Study at a Rural Teaching College in Central India

Background The high prevalence of thyroid dysfunction in patients with chronic kidney disease (CKD) indicates a major correlation between the progression of CKD and thyroid dysfunction. In this study, we highlighted thyroid dysfunction and its relation to the severity and different stages of CKDs. Materials and methods From October 2018 to September 2020, 200 cases with CKD, admitted under the Department of Medicine at a rural teaching hospital in central India, were selected for the study. The collected data was analyzed and correlated using the Chi-square test, and the parameters suggested the presence or absence of low T3 syndrome, low T4 syndrome, and primary hypothyroidism. Results Out of 200 patients enrolled, 181 (91.5%) had thyroid abnormalities. Among these patients, the presence of low T3 syndrome was 57%, low T4 syndrome was 23%, and primary hypothyroidism was 10.5%. It was reported that as the CKD stages advanced, TSH levels increased with a statistically significant difference (p=0.04). Conclusions As kidney function progressively deteriorated, specifically in stage five, the chances of occurrence of hypothyroidism increased.

Endocrinological disorders in acute kidney injury: an often overlooked field of clinical research

Acute kidney injury (AKI) is a common comorbidity, affecting approximately one in five hospitalized adults. The kidney is the site for the production, metabolism or excretion of most hormones, including the production of erythropoietin (EPO), the active form of vitamin D, renin, thrombopoietin, and the excretion of insulin, catecholamines, gastrin and many other hormones. Therefore, it is reasonable to say that AKI can have a considerable impact on the endocrine system. Although the effects of AKI on various parameters, including cardiovascular parameters, serum electrolytes and acid-base disorders, neuro-humoral mechanisms and neurological outcomes have been extensively studied, the endocrinological consequences of AKI are understudied. Thyroid dysfunction, mainly euthyroid sick syndrome, hypo/hyperglycemia, bone mineral disorders, changes in EPO and atrial natriuretic peptide (ANP) levels are commonly found in AKI. EPO, thyroxine and ANP administration have been evaluated as potential tools to prevent or treat AKI with varying success, while the effects of AKI on some key hormones, including cortisol and insulin, have never been studied. Aim of this narrative review is to illustrate what is known and what is not known about the endocrinological outcomes of AKI. Few clinical trials are ongoing: however, there is a clear need for large-scale randomized controlled trials investigating the endocrinological consequences of AKI.

Hyperthyroid cats and their kidneys: a literature review

Hyperthyroidism and chronic kidney disease (CKD) are common diseases of geriatric cats, and often occur concurrently. Thus, a thorough understanding of the influence of thyroid function on renal function is of significant value for all feline practitioners. Among other effects, hyperthyroidism causes protein catabolism and increases renal blood flow and glomerular filtration rate (GFR). These effects render traditional renal markers insensitive for the detection of CKD in cats with uncontrolled hyperthyroidism. Furthermore, the development of iatrogenic hypothyroidism with over treatment of hyperthyroidism can be detrimental to renal function and may negatively affect long-term survival. This review discusses important diagnostic considerations of feline hyperthyroidism, as well as key treatment modalities, with an emphasis on the use of radioiodine and the importance of post treatment monitoring of thyroid and renal parameters. In Australia, a common curative treatment for cats with benign hyperthyroidism (i.e. thyroid hyperplasia or adenoma) is a fixed dose of orally administered radioiodine, regardless of the serum total thyroxine concentration at the time of diagnosis. This review discusses the long term outcomes of this standard of care in comparison with current, relevant research literature from around the world. Finally, this review explores the use of symmetric dimethylarginine (SDMA) in assessing renal function before and after treatment in hyperthyroid cats. SDMA correlates well with GFR and creatinine in non-hyperthyroid cats, but our understanding of its performance in hyperthyroid cats remains in its infancy.

Relationship between autoimmune thyroid disease and nephropathy: A clinicopathological study

The association of nephropathy with autoimmune thyroid disease (AITD) has been reported previously. However, there is limited information on the relationship between thyroid autoantibodies and nephropathy. A retrospective study was conducted using the medical records of 246 patients with nephropathy, 82 of whom had concurrent AITD. General characteristics, thyroid function, autoantibodies, and the pathological types of nephropathy were analyzed. Immunohistochemistry was used to detect the thyroglobulin antibody (TG-Ab) and thyroid peroxidase antibody (TPO-Ab) in the kidneys. We found nephropathy patients with AITD exhibited higher serum levels of TPO-Ab, TG-Ab, thyroid-stimulating hormone receptor antibody (TR-Ab), and immunoglobulin G (IgG) (P < .05). Compared with the nephropathy without AITD group, the nephropathy with AITD group exhibited higher proportions of membranous nephropathy (MN) and focal segmental glomerulosclerosis (FSGS), and relatively lower proportions of mesangial proliferative glomerulonephritis (MsPGN) and minimal change nephropathy (MCN) (P = .005). TPO-Ab and TG-Ab levels in the kidney were more prevalent in nephropathy patients with AITD than those without AITD (P = .015 and P = .026, respectively). Subgroup analysis demonstrated that serum levels of thyroid stimulating hormone (TSH), TG-Ab, TPO-Ab, immunoglobulin M (IgM), and IgG in the MN group were significantly higher, whereas the levels of free thyroxine (FT4) and estimated glomerular filtration rate (eGFR) were lower, as compared with MN with Hashimoto thyroiditis (HT) group (P < .05). TPO-Ab and TG-Ab expression levels in the kidneys were more prevalent in the MN group than in the MN with HT group (P = .034). The expression levels of FT4, TG-Ab, TPO-Ab, and thyroid-stimulating hormone receptor antibody (TSHR-Ab) in the serum were significantly higher in the MN group than in the MN with Graves disease (GD) group (P < .05). The expression of TPO-Ab in the kidneys was more prevalent in the MN group than in the MN with GD group (P = .011). In sum, the expressions of TPO-Ab and TG-Ab were more prevalent in the kidneys of patients with nephropathy and AITD. Our findings indicate that TPO-Ab and TG-Ab may play a role in the development of AITD-related nephropathy.

Liver-type fatty acid-binding protein and neutrophil gelatinase-associated lipocalin in cats with chronic kidney disease and hyperthyroidism

BACKGROUND

Liver-type fatty acid-binding protein (L-FABP) and neutrophil gelatinase-associated lipocalin (NGAL) are candidate biomarkers for the detection of early chronic kidney disease (CKD) in cats.

OBJECTIVE

To evaluate urinary and serum L-FABP and NGAL concentrations in CKD cats and in hyperthyroid cats before and after radioiodine (¹³¹ I) treatment.

ANIMALS

Nine CKD cats, 45 healthy cats and hyperthyroid cats at 3 time points including before (T0, n = 49), 1 month (T1, n = 49), and 11 to 29 months after (T2, n = 26) ¹³¹ I treatment.

METHODS

Cross-sectional and longitudinal study. Serum L-FABP (sL-FABP), serum NGAL (sNGAL), urinary L-FABP (uL-FABP), and urinary NGAL (uNGAL) were compared between the 3 groups and between hyperthyroid cats before and after treatment. Data are reported as median (min-max).

RESULTS

CKD cats had significantly higher sL-FABP (13.50 [3.40-75.60] ng/ml) and uL-FABP/Cr (4.90 [0.97-2139.44] µg/g) than healthy cats (4.25 [1.34-23.25] ng/ml; P = .01 and 0.46 [0.18-9.13] µg/g; P < .001, respectively). Hyperthyroid cats at T0 had significantly higher uL-FABP/Cr (0.94 [0.15-896.00] µg/g) than healthy cats (P < .001), thereafter uL-FABP/Cr significantly decreased at T2 (0.54 [0.10-76.41] µg/g, P = .002). For the detection of CKD, uL-FABP/Cr had 100% (95% confidence interval [CI], 66.4-100.0) sensitivity and 93.2% (95% CI, 81.3-98.6) specificity. There were no significant differences in sNGAL and uNGAL/Cr between the 3 groups.

CONCLUSIONS AND CLINICAL IMPORTANCE

L-FABP, but not NGAL, is a potential biomarker for the detection of early CKD in cats. Utility of uL-FABP to predict azotemia after treatment in hyperthyroid cats remains unknown.

Thyroid function, renal events and mortality in chronic kidney disease patients: the German Chronic Kidney Disease study

BACKGROUND

Hypothyroidism and low free triiodothyronine (FT3) syndrome [low FT3 levels with normal thyroid-stimulating hormone (TSH)] have been associated with reduced kidney function cross-sectionally in chronic kidney disease (CKD) patients with severely reduced estimated glomerular filtration rate (eGFR) or end-stage kidney disease (ESKD). Results on the prospective effects of impaired thyroid function on renal events and mortality for patients with severely reduced eGFR or from population-based cohorts are conflicting. Here we evaluated the association between thyroid and kidney function with eGFR (cross-sectionally) as well as renal events and mortality (prospectively) in a large, prospective cohort of CKD patients with mild to moderately reduced kidney function.

METHODS

Thyroid markers were measured among CKD patients from the German Chronic Kidney Disease study. Incident renal endpoints (combined ESKD, acute kidney injury and renal death) and all-cause mortality were abstracted from hospital records and death certificates. Time to first event analysis of complete data from baseline to the 4-year follow-up (median follow-up time 4.04 years) of 4600 patients was conducted. Multivariable linear regression and Cox proportional hazards models were fitted for single and combined continuous thyroid markers [TSH, free thyroxine (FT4), FT3] and thyroid status.

RESULTS

Cross-sectionally, the presence of low-FT3 syndrome showed a significant inverse association with eGFR and continuous FT3 levels alone showed a significant positive association with eGFR; in combination with FT4 and TSH, FT3 levels also showed a positive association and FT4 levels showed a negative association with eGFR. Prospectively, higher FT4 and lower FT3 levels were significantly associated with a higher risk of all-cause mortality (N events = 297). Per picomole per litre higher FT3 levels the risk of reaching the composite renal endpoint was 0.73-fold lower (95% confidence interval 0.65-0.82; N events = 615). Compared with euthyroid patients, patients with low-FT3 syndrome had a 2.2-fold higher risk and patients with hypothyroidism had a 1.6-fold higher risk of experiencing the composite renal endpoint.

CONCLUSIONS

Patients with mild to moderate CKD suffering from thyroid function abnormalities are at an increased risk of adverse renal events and all-cause mortality over time.

Proteinuria in Severe Hypothyroidism: A Prospective Study

CONTEXT

Hypothyroidism is associated with reversible decline in kidney function as measured by estimated glomerular filtration rate (eGFR). eGFR and proteinuria are the most important markers for clinical assessment of kidney function. Though hypothyroidism is associated with proteinuria in cross-sectional data, the impact of treatment on proteinuria is unknown.

OBJECTIVE

This study explores the effect of thyroid hormone replacement therapy on eGFR and 24-hour urine protein excretion in patients with severe primary hypothyroidism.

DESIGN AND PARTICIPANTS

This study was a prospective, observational cohort study in adults with severe primary hypothyroidism (serum thyrotropin [TSH] > 50 µIU/mL). Individuals with preexisting or past kidney disease, kidney or urinary tract abnormalities, calculi or surgery, diabetes mellitus, or hypertension were excluded. The participants received thyroid hormone replacement therapy. Thyroid functions, eGFR, 24-hour urine protein excretion, and biochemical parameters were measured at baseline and 3 months.

SETTING

This study took place at a single center, a tertiary care referral and teaching hospital.

RESULTS

Of 44 enrolled participants, 43 completed 3 months of follow-up. At 3 months, serum TSH levels decreased and thyroxine levels increased (P < .001 for both). Significant increases in eGFR (mean difference, 18.25 ± 19.49 mL/min/1.73 m2; 95% CI, 12.25 to 24.25, P < .001) and declines in 24-hour urine protein excretion (mean difference, -68.39 ± 125.89 mg/day; 95% CI, -107.14 to -29.65, P = .001) were observed. Serum cholesterol and low-density lipoprotein levels also significantly decreased (P < .001).

CONCLUSIONS

Thyroid hormone replacement therapy in patients with severe primary hypothyroidism improves eGFR and decreases 24-hour urine protein excretion, thereby suggesting reversible alterations.

A Pilot Trial on the Effect of Levothyroxine on Proteinuria in Patients With Advanced CKD

INTRODUCTION

Thyroid hormones can directly affect kidney function; elevated levels of thyroid-stimulating hormone (TSH) and chronic kidney disease (CKD) are associated with proteinuria, decreased estimated glomerular filtration rate (eGFR), and progression to end-stage renal disease. Our hypothesis is that in patients with CKD and TSH at levels considered to be in the low subclinical hypothyroidism (SCH) range, lowering TSH with levothyroxine (LVX) improves the clinical parameters of renal function.

METHODS

This was a double-blind, randomized, pilot clinical trial in patients with proteinuric CKD (eGFR <60 ml/min per 1.73 m2 and proteinuria >150 mg/d) performed at the Hospital Civil de Guadalajara, with the intention of lowering TSH (levels of 1.25-2.5 μIU/l) in patients with TSH (levels of 2.6-9.9 μIU/ml with FT4 in the range of 0.7-1.8 ng/dl). Patients were randomized 1:1 to receive LVX or placebo for 12 weeks. The primary objective was to evaluate absolute levels of proteinuria at the beginning compared to the end of the study and, as a secondary objective, the changes in serum creatinine (sCr), eGFR, cholesterol, triglycerides, low-density lipoprotein (LDL), and blood pressure, and to assess the tolerability and safety of LVX.

RESULTS

Between March and November 2018, a total of 163 patients were assessed for eligibility; 119 patients did not meet the inclusion criteria or were excluded, and 32 patients were randomized. The demographic and clinical characteristics of the 2 study groups were essentially not different. Subjects were 66.87 (SD 12.19) years of age, 62.5% were female, 75% were diabetes mellitus, eGFR was 23.55 (±12.91) ml/min per 1.73 m2, TSH was 5.37 ± 2.13 μIU/ml, proteinuria in 24-hour urine collection was 1.52 ± 1.12, and all of them were taking angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs). Proteinuria at 12 weeks in the LVX group was 0.89 SD ± 1.28 g/d, and in the placebo group it was 1.35 SD ± 0.85 g/d; when compared to placebo, LVX showed a significant decrease in proteinuria of 1.1 g/d (P = 0.0011). The eGFR in the LVX group showed an improvement of 4 ml/min/1.73 m2 (P = 0.049); in the placebo group, there was a decrease of 1.98 ml/min per 1.73 m2. The sCr, cholesterol, triglycerides, low-density lipoprotein, systolic blood pressure, and diastolic blood pressure were not different between groups. Adverse events were reported in the LVX group in 7.14% of patients and in 11.11% of patients in the placebo group; none left the study because of adverse effects, and there were no serious adverse events.

CONCLUSION

This single-center, randomized, double-blind, placebo-controlled pilot clinical trial in patients with advanced proteinuric CKD who already used ACEIs or ARBs demonstrated that administering LVX to obtain a TSH range close to 2.5 μIU/ml decreased proteinuria and improved eGFR. Future research is needed to confirm our results and to determine whether our findings generalize to patient groups not explicitly enrolled in this small pilot trial.

Symmetric dimethylarginine concentrations in dogs with hypothyroidism before and after treatement with levothyroxine

OBJECTIVES

To evaluate the serum symmetric dimethylarginine (SDMA) and serum creatinine concentrations in a population of hypothyroid dogs at the time of diagnosis and after treatment.

MATERIALS AND METHODS

Serum SDMA and serum creatinine were measured in serum samples of 24 healthy dogs and 24 hypothyroid dogs, at the time of diagnosis (T0) and after supplementation with levothyroxine (T1).

RESULTS

The mean SDMA concentrations (reference intervals [RI] <18 μg/dL and <14 μg/dL depending on the source) were 11.7 ± 3.5 μg/dL, 13.8 ± 3.1 μg/dL and 11.83 ± 2.87 μg/dL in healthy dogs, and in the hypothyroid dogs at T0 and T1, respectively. The SDMA concentrations were higher in the hypothyroid dogs at T0 in comparison with the healthy dogs. Of the hypothyroid dogs, 1 out of 24 had an SDMA concentration above 18 μg/dL and 12 out of 24 above 14 μg/dL at T0. At T1, none of the hypothyroid dogs had SDMA concentrations above 18 μg/dL and two of them had SDMA concentrations above 14 μg/dL. The serum creatinine concentration was higher in the hypothyroid dogs at T0 as compared to the healthy dogs. At T0, 8 out of 24 hypothyroid dogs had serum creatinine concentrations above the RI (>1.4 mg/dL). In all but one dog, serum creatinine normalised after treatment.

CLINICAL SIGNIFICANCE

The SDMA and serum creatinine concentrations were higher in hypothyroid dogs at diagnosis as compared to healthy dogs. Serum creatinine concentrations were increased in one-third of the hypothyroid dogs and in the majority of cases normalised after levothyroxine supplementation. SDMA concentrations were rarely above the upper limit of the RI when the higest (<18 μg/dL) cut-off was employed. The diagnostic accuracy of SDMA in dogs with thyroid dysfunction requires additional evaluation.

Pharmacokinetic bias analysis of an association between clinical thyroid disease and two perfluoroalkyl substances

Exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) has been associated with the occurrence of thyroid disease in some epidemiologic studies. We hypothesized that in a specific epidemiologic study based on the National Health and Nutrition Examination Survey, the association of clinical thyroid disease with serum concentration of PFOA and PFOS was due to reverse causality. Thyroid hormone affects glomerular filtration, which in turn affects excretion of PFOA and PFOS. We evaluated this by linking a model of thyroid disease status over the lifetime to a physiologically based pharmacokinetic model of PFOA and PFOS. Using Monte Carlo methods, we simulated the target study population and analyzed the data using multivariable logistic regression. The target and simulated populations were similar with respect to age, estimated glomerular filtration rate, serum concentrations of PFOA and PFOS, and prevalence of clinical thyroid disease. The analysis showed little or no evidence of bias from the hypothesized mechanism. The largest bias was for the fourth quartile of PFOA in females, with an odds ratio of 0.93 (95% CI, 0.90, 0.97). The reported odds ratio of clinical thyroid disease for this group was 1.63 (1.07, 2.47), and if it were corrected for the bias would have been 1.74 (1.14, 2.65). Our results suggest that little of the reported association in the target study was due to reverse causality.

Quantitative bias analysis of the association between subclinical thyroid disease and two perfluoroalkyl substances in a single study

Exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) has been associated with the occurrence of thyroid disease in some epidemiologic studies. We hypothesized that in a specific epidemiologic study based on the National Health and Nutrition Examination Survey, the association of subclinical thyroid disease with serum concentration of PFOA and PFOS was due to reverse causality. Thyroid hormone affects glomerular filtration, which in turn affects excretion of PFOA and PFOS. We evaluated this by linking a model of thyroid disease status over the lifetime to physiologically based pharmacokinetic models of PFOA and PFOS. Using Monte Carlo methods, we simulated the target study population and analyzed the data using multivariable logistic regression. The target and simulated populations were similar with respect to age, estimated glomerular filtration rate, serum concentrations of PFOA and PFOS, and prevalence of subclinical thyroid disease. Our findings suggest that in the target study the associations with subclinical hypothyroidism were overstated and the results for subclinical hyperthyroidism were, in general, understated. For example, for subclinical hypothyroidism in men, the reported odds ratio per ln(PFOS) increase was 1.98 (95% CI 1.19-3.28), whereas in the simulated data the bias due to reverse causality gave an odds ratio of 1.19 (1.16-1.23). Our results provide evidence of bias due to reverse causality in a specific cross-sectional study of subclinical thyroid disease with exposure to PFOA and PFOS among adults.

The Role of Selenium in Oxidative Stress and in Nonthyroidal Illness Syndrome (NTIS): An Overview

Selenium is a trace element, nutritionally classified as an essential micronutrient, involved in maintaining the correct function of several enzymes incorporating the selenocysteine residue, namely the selenoproteins. The human selenoproteome including 25 proteins is extensively described here. The most relevant selenoproteins, including glutathione peroxidases, thioredoxin reductases and iodothyronine deiodinases are required for the proper cellular redox homeostasis as well as for the correct thyroid function, thus preventing oxidative stress and related diseases. This review summarizes the main advances on oxidative stress with a focus on selenium metabolism and transport. Moreover, thyroid-related disorders are discussed, considering that the thyroid gland contains the highest selenium amount per gram of tissue, also for future possible therapeutic implication.

Effect of Thyroid Hormones on Kidney Function in Patients after Kidney Transplantation

Elevated levels of thyroid-stimulating-hormone (TSH) are associated with reduced glomerular filtration rate (GFR) and increased risk of developing chronic kidney disease even in euthyroid patients. Thyroid hormone replacement therapy has been shown to delay progression to end-stage renal disease in sub-clinically hypothyroid patients with renal insufficiency. However, such associations after kidney transplantation were never investigated. In this study the association of thyroid hormones and estimated GFR (eGFR) in euthyroid patients after kidney transplantation was analyzed. In total 398 kidney transplant recipients were assessed retrospectively and association between thyroid and kidney function parameters at and between defined time points, 12 and 24 months after transplantation, was studied. A significant inverse association was shown for TSH changes and eGFR over time between months 12 and 24 post transplantation. For each increase of TSH by 1 µIU/mL, eGFR decreased by 1.34 mL/min [95% CI, −2.51 to −0.16; p = 0.03], corresponding to 2.2% eGFR decline, within 12 months. At selected time points 12 and 24 months post transplantation, however, TSH was not associated with eGFR. In conclusion, an increase in TSH between 12 and 24 months after kidney transplantation leads to a significant decrease in eGFR, which strengthens the concept of a kidney-thyroid-axis.

Influence of low free thyroxine on progression of chronic kidney disease

BACKGROUND

Hypothyroidism is highly prevalent in patients with chronic kidney disease (CKD) and has been associated with poorer clinical outcomes, including faster decline of kidney function. However, there is no consensus whether low free thyroxin (LFT) affects the rate of estimated glomerular filtration rate (eGFR) decline and how the presence of proteinuria influences the progression of renal dysfunction in hypothyroidism.

METHODS

We assessed thyroid status, proteinuria, and progression of eGFR by Modification of Diet in Renal Disease equation and CKD-EPI equation in a cohort of CKD patients followed in general nephrology clinics. We estimated the association of LFT levels, and the degree of proteinuria on progression of eGFR. We adjusted for other covariables: age, gender, body mass index, diabetes, hypertension, HbA1c, uric acid, cholesterol, and triglycerides levels..

RESULTS

One thousand six hundred ten patients (64 ± 15 years, 46.8% men, 25.3% diabetic) were included. At beggnining of follow up eGFR was between 45 and 60, 30-45 and 15-30 ml/min/1.73m2 in 479 (29.8%), 551(34.2%), and 580(36.0%) patients, respectively. LFT levels were available at initial evaluation in 288(17.9%) patients and 735(48.5%) had assessment of proteinuria (19.6% with LFT vs. 15.4% without LFT, p = 0.032). Median follow-up time was of 21 months, and 1223(76%) had at least 1 year of follow up. Overall, eGFR decline per month was - 0.05(- 0.26, 0.23) ml/min/1.73m2, reaching 1.7(1.3, 2.4) ml/min/1.73m2 by the end of study period. Similar results were obtained using CKD-EPI. Multivariable mixed linear analysis showed that proteinuria and age were independently associated with eGFR decline, with no effect of LFT, and no interaction between proteinuria and LFT. In patients without proteinuria, there was an improvement of eGFR despite the presence of LFT.

CONCLUSIONS

We confirmed a faster rate of eGFR declined in patients with proteinuria. However, despite the pathophysiological rational that hypothyroidism can lead to increased rate of CKD progression, we failed to demonstrate an association between LFT and rate of CKD progression. We conclude that the benefit of hypothyroidism treatment in CKD patients needs to be evaluate in prospective studies.

Prevalence of iatrogenic hypothyroidism in hyperthyroid cats treated with radioiodine using an individualised scoring system

OBJECTIVES

The aim of this study was to report the prevalence of iatrogenic hypothyroidism, with or without azotaemia, based on the measurement of serum total thyroxine (T4), thyroid-stimulating hormone (TSH) and creatinine concentrations, in hyperthyroid cats undergoing radioiodine (131I) treatment where the 131I dose was calculated using a previously described scoring system. A secondary aim of the study was to determine the positive and negative predictive values of serum T4 and TSH concentrations obtained 19 days after treatment in order to predict the development of iatrogenic hypothyroidism 6-9 months after 131I treatment.

METHODS

Serum T4, TSH and creatinine concentrations were measured 19 days and 6-9 months after 131I treatment. The prevalence of iatrogenic hypothyroidism was assessed with the results obtained 6-9 months after 131I treatment.

RESULTS

The prevalence of overt and subclinical hypothyroidism 6-9 months after 131I treatment was 40.0% (22/55 cats) and 12.7% (7/55 cats). Overt hypothyroidism with azotaemia was diagnosed in 8/55 (14.5%) cats. The positive and negative predictive values for the prediction of the development of iatrogenic hypothyroidism 6-9 months after 131I treatment were 72.2% and 80.0%, respectively, for a low serum T4 concentration, and 75.0% and 44.6%, respectively, for an increased serum TSH concentration.

CONCLUSIONS AND RELEVANCE

The use of an individualised scoring system is effective in determining the 131I dose for the treatment of hyperthyroid cats. However, the prevalence of overt hypothyroidism was higher in comparison with other studies using different dosing protocols. Further studies comparing the efficacy of individualised scoring systems and different fixed doses to determine which method is superior are warranted.

Chronic kidney disease in cats attending primary care practice in the UK: a VetCompassTM study

Chronic kidney disease (CKD) is a frequent diagnosis in cats attending primary care practice and the most frequent cause of death in cats aged over five years, yet there is limited published research for CKD in cats attending primary care practice. This study aimed to estimate the prevalence of CKD and investigate risk factors for diagnosis and survival of cats diagnosed with CKD in UK primary care practices. The study included cats attending VetCompass^TM practices from January 1, 2012 to December 31, 2013. A nested case-control and cohort study were undertaken. From 353,448 cats attending 244 clinics, the prevalence of CKD was estimated as 1.2 per cent (95 per cent CI 1.1 per cent to 1.3 per cent). Most cats with CKD had clinical signs at diagnosis (66.6 per cent). Few cats underwent investigations or monitoring of serum creatinine (32.6 per cent), urine protein:creatinine ratio (14.9 per cent) or blood pressure measurement (25.6 per cent). A proprietary renal diet was the most frequently prescribed management (63.8 per cent). Median survival time following diagnosis was 388 days (IQR 88-1042 days). This study provides generalisable evidence from the wider cat population to aid veterinarians in improved diagnosis and management of CKD that can benefit the health and welfare of cats with CKD in the UK.

Changes in thyroid and renal function after bilateral thyroidectomy in cats

BACKGROUND

Iatrogenic hypothyroidism might worsen the prognosis of cats with azotemic CKD after thyroidectomy. Varying thyroxine concentrations influence utility of creatinine in assessing renal function. Symmetric dimethylarginine (SDMA) has limited studies in cats with changing thyroid status.

OBJECTIVES

Thyroid status is stable 6 months post-thyroidectomy. Symmetric dimethylarginine and creatinine are linearly associated without influence from total thyroxine concentration (tT4).

ANIMALS

Electronic records of 2 first opinion practices were searched using the term "thyroidectomy" to include 81 client-owned cats that had undergone bilateral thyroidectomy.

METHODS

Retrospective cross-sectional study assessing thyroid hormone concentrations of 68 cats within 6 months of surgery. A longitudinal study of thyroid status in 23 cats with >18 months follow-up post-thyroidectomy. A generalized estimating equation assessed the associations of bodyweight, tT4 and creatinine concentrations on SDMA concentration.

RESULTS

Sixty-eight cats had follow-up within 6 months. Fifteen cats (22%) had persistent, or recurrent, hyperthyroidism and 33 cats (49%) were hypothyroid. Twenty-three of the euthyroid/hypothyroid cats had long-term follow-up (595-1955 days); 4 cats (17%) remained hypothyroid, 19 cats (83%) were euthyroid (often transiently), and 9 of 23 cats (44%) developed recurrent hyperthyroidism. Symmetric dimethylarginine and creatinine were linearly associated, but hyperthyroid cats had higher SDMA concentrations, relative to creatinine (P = .003).

CONCLUSIONS AND CLINICAL IMPORTANCE

Cats have changes in thyroid function for years after bilateral thyroidectomy, with a high incidence of recurrent hyperthyroidism. Both SDMA and creatinine are affected by thyroxine concentrations, and the effect is greater in hyperthyroid cats.

Assessment of symmetric dimethylarginine as a biomarker of renal function in hyperthyroid cats treated with radioiodine

Background

Measurement of serum creatinine (sCr) and urea nitrogen fail to detect decreased renal function in many hyperthyroid cats because of low muscle mass and glomerular hyperfiltration of affected cats. Serum symmetric dimethylarginine (sSDMA) is an earlier and more sensitive renal biomarker than sCr.

Objective

Evaluate sSDMA as a biomarker of renal function in hyperthyroid cats before (T0) and 1 month after (T1) radioiodine (¹³¹I) treatment.

Animals

Forty‐seven client‐owned hyperthyroid nonazotemic cats were evaluated at T0 and T1.

Methods

A prospective study in which sCr and sSDMA concentrations were determined in 47 hyperthyroid cats at T0 and at T1. Glomerular filtration rate (GFR) was estimated at T0 and T1 in 10 of these 47 cats using plasma exogenous creatinine clearance test.

Results

Serum SDMA was elevated (>14 μg/dL) in 6 of 47 cats at T0 and normalized after treatment in 4 of those cats. All cats remained nonazotemic after treatment. In 10 cats in which GFR was measured, correlation between GFR and sSDMA was low and not significant (τ_b = −0.35, P = .17 at T0 and τ_b = −.22, P = .41 at T1), whereas correlation between GFR and sCr was moderate and significant (τ_b = −0.52, P < .05 at T0 and τ_b = −.53, P = <.05 at T1).

Conclusions and Clinical Importance

Careful interpretation of mildly increased sSDMA with normal sCr in hyperthyroid cats is warranted as sSDMA values might normalize after resolution of hyperthyroidism in some cats. In this population of hyperthyroid cats, sSDMA was poorly correlated with GFR.

Spontaneous primary hypothyroidism in 7 adult cats

BACKGROUND

Naturally occurring hypothyroidism in adult cats is rare, with only 4 cases reported.

OBJECTIVES

To describe the historical, clinical, laboratory, and scintigraphic features of adult cats with spontaneous hypothyroidism.

ANIMALS

Seven adult cats referred for suspected hypothyroidism.

METHODS

Prospective case series. We collected data on cats' signalment, clinical signs, results of physical examination, routine laboratory and thyroid hormone testing, and thyroid imaging (thyroid scintigraphy or ultrasound). We subsequently treated cats with levothyroxine and evaluated their response to treatment.

RESULTS

Cats ranged from 3.5 to 11 years, with no apparent breed predilection; 6/7 cats were male. Only 2/7 cats were initially tested because of signs of hypothyroidism (hair-coat changes, lethargy, obesity); others were tested for routine thyroid monitoring or palpable thyroid nodules. Four were azotemic (serum creatinine, 2.2-3.4 mg/dL). Six of the cats had low serum thyroxine (T4 ) and free T4 (fT4 ) concentrations, whereas all 7 cats had high thyroid-stimulating hormone (TSH) concentrations. In 6/7 cats, thyroid scintigraphy revealed bilateral goiter with intense radionuclide uptake; imaging showed no visible thyroid tissue in the other. After levothyroxine treatment, serum concentrations of T4 and fT4 increased and TSH fell; high serum creatinine normalized in azotemic cats; and repeat imaging showed reduction in goiter size.

CONCLUSIONS AND CLINICAL IMPORTANCE

Primary hypothyroidism develops in adult cats, with a higher prevalence than previously thought. Most cats appear to develop a goitrous form of hypothyroidism associated with thyroid hyperplasia, whereas thyroid atrophy appears to be less common. With levothyroxine replacement, clinical and laboratory abnormalities improve or resolve.

Changes in the thyroid hormone profiles in children with nephrotic syndrome

Purpose

We compared thyroid hormone profiles in children with nephrotic syndrome (NS) during the nephrotic phase and after remission.

Methods

This study included 31 pediatric NS patients. The thyroid hormone profiles included serum levels of triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), and free T4.

Results

Of the 31 patients, 16 (51.6%) showed abnormal thyroid hormone profiles: 6 had overt hypothyroidism, 8 had subclinical hypothyroidism, and 2 had low T3 syndrome. The mean serum T3, T4, and free T4 levels in the nephrotic phase and after remission were 82.37±23.64 and 117.88±29.49 ng/dL, 5.47±1.14 and 7.91±1.56 µg/dL, and 1.02±0.26 and 1.38±0.23 ng/dL, respectively; the levels were significantly lower in the NS nephrotic phase (P=0.0007, P<0.0001, and P=0.0002). The mean serum TSH levels during the nephrotic phase and after remission were 8.05±3.53 and 4.08±2.05 µIU/ mL, respectively; they were significantly higher in the nephrotic phase (P=0.0005). The urinary protein/ creatinine ratio during the nephrotic phase was significantly correlated with serum T3, T4, and free T4 levels (r=-0.5995, P=0.0032; r=-0.5797, P=0.0047; r=-0.5513, P=0.0078) as well as with TSH levels (r=0.5022, P=0.0172). A significant correlation was found between serum albumin and serum T3 levels during the nephrotic phase (r=0.5385, P=0.0018) but not between serum albumin and T4, TSH, or free T4 levels. These significant correlations all disappeared after remission.

Conclusion

Abnormal thyroid hormone profile findings were observed in 51.6% of pediatric patients with NS. Thyroid hormone levels normalized after remission, regardless of levothyroxine therapy.

Relationship between serum thyrotropin and urine albumin excretion in euthyroid subjects with diabetes

BACKGROUND

Microalbuminuria represents vascular and endothelial dysfunction. Thyroid hormones can influence urine albumin excretion as it exerts crucial effects on the kidney and on the vascular system. This study explores the relationship between serum thyrotropin and urine albumin excretion in euthyroid patients with diabetes.

METHODS

A total of 433 patients with type 1 or 2 diabetes were included in this retrospective cross-sectional study. Data included anthropometric measurements and biochemical parameters from diabetes clinic. Males with urine albumin creatinine ratio >2.5 and female's >3.5 mg/mmoL were considered to have microalbuminuria.

RESULTS

34.9% of the patients had microalbuminuria. Prevalence of microalbuminuria increased according to TSH quartiles (26.9, 34.6, 38.5 and 44.9%, P for trend = 0.02). In a fully adjusted logistic regression model, higher TSH concentrations were associated with high prevalence of microalbuminuria (adjusted odds ratio 2.06 [95% CI: 1.14-3.72]; P = 0.02), while comparing the highest with the lowest quartile of TSH. Multiple linear regression analysis showed an independent association between serum TSH and urine albumin creatinine ratio (β = 0.007, t = 2.03 and P = 0.04). The risk of having microalbuminuria was higher with rise in TSH concentration in patients with younger age (<65 years), raised body mass index (≥25 kg/m²), hypertension, type 2 diabetes and hyperlipidaemia and age was the most important determinant ( P for interaction = 0.02).

CONCLUSION

Serum TSH even in the euthyroid range was positively associated with microalbuminuria in euthyroid patients with diabetes independent of traditional risk factors. This relationship was strongest in patients with components of the metabolic syndrome.

Predictive value of scintigraphic (semi-)quantitative thyroid parameters on radioiodine therapy outcome in hyperthyroid cats

Objectives The outcome of radioiodine therapy in hyperthyroid cats is suspected to be influenced by multiple factors. The degree of activity of the thyroid gland, represented by uptake of sodium pertechnetate or tracer activities of radioiodine by the thyroid gland on thyroid scintigraphy, has been suggested in the literature as one of those. Thyroid gland pertechnetate uptake can be represented by (semi-)quantitative factors such as the thyroid to salivary gland (T/S) ratio, the thyroid to background (T/B) ratio and the percentage technetium uptake by the thyroid glands (%TcU). The aim of this study was to investigate a possible relationship between these thyroid scan parameters and radioiodine therapy outcome. Methods Sodium pertechnetate thyroid scans of 75 hyperthyroid cats were retrospectively evaluated and statistical analysis was performed with and without correction for injected radioiodine activity. Three different background regions of interest (ROIs) were used to calculate the T/B ratio and %TcU: 'neck', 'circle' and 'copy ROI'. Results Higher T/S ratios were found to be significantly related to a persistent hyperthyroid outcome in both analyses. For the T/S ratio, a threshold value of 5.4 was determined, with a sensitivity of 73% and a specificity of 59%. An increased risk for persistent hyperthyroidism compared with a final euthyroid outcome with an increased T/Bcircle ratio was only found to be significant without correction for the activity of radioiodine administered. For the %TcU no statistical significance was reached. Regarding a low total thyroxine outcome, no significant relationships with any of the investigated parameters were found. Conclusions and relevance The findings of this study suggest that semi-quantification of thyroid gland uptake is best performed using the T/S ratio. A T/S ratio ⩾5.4 is a possible indicator for an increased risk of persistent hyperthyroidism.

The relationship between subclinical hypothyroidism and serum levels of uric acid and creatinine in children aged 2-14 years

PURPOSE

Hypothyroidism is a clinical syndrome that can lead to elevated levels of serum creatinine and uric acid by causing impaired renal function. Although many studies have been carried out on the relationship between overt hypothyroidism and renal function, few studies have been conducted on subclinical hypothyroidism and renal function, especially in pediatric patients. For this reason, we studied this issue in children, so as to provide a background for more useful research and future education.

METHODS

This case-control study was performed on 107 children aged 2-14 years, 56 children with subclinical hypothyroidism in the case group, and 51 healthy children in the control group presenting to Ayatollah Mousavi Hospital in Zanjan and private clinics of Zanjan city. Thyroid stimulating hormone, triiodothyronine, thyroxine, creatinine, and uric acid were measured in both groups of children after obtaining the necessary criteria for entering the study.

RESULTS

Compared to the control group, subjects with subclinical hypothyroidism had higher levels of creatinine (P=0.003), while serum uric acid levels in subclinical hypothyroid children was not significantly different from those in the control group (P=0.200).

CONCLUSIONS

In subclinical hypothyroidism in children, creatinine was higher than in euthyroid patients, but uric acid was not different.

Insulin-like growth factor type 1 concentrations in hyperthyroid cats before and after treatment with thiamazole

Objectives The aim of this study was to evaluate changes in circulating insulin-like growth factor type 1 (IGF-1) concentrations in hyperthyroid cats, before and after thiamazole treatment. Methods Thirty-four hyperthyroid cats were retrospectively included. Plasma free thyroxine (fT4) and IGF-1 concentrations were measured at diagnosis and 3 months after initiating antithyroid drug therapy. Results Median fT4 significantly decreased ( P <0.001) after treatment (from 78 pmol/l [range 43-122 pmol/l] to 31 pmol/l [range below assay limit of detection to 88 pmol/l]), whereas IGF-1 values significantly increased ( P <0.001) after treatment (from 117 ng/ml [33-341 ng/ml] to 221 ng/ml [36-865 ng/ml]). fT4 and IGF-1 concentrations were significantly negatively correlated both at diagnosis (r = -0.43, P = 0.01) and after treatment (r = -0.51, P = 0.002). Conclusions and relevance In cats, IGF-1 concentrations appear to be inversely proportional to the severity of hyperthyroidism and significantly increase after treatment with thiamazole.

Impact of the Amount of Liquid Intake on the Dose Rate of Patients Treated with Radioiodine

PURPOSE

Despite therapeutic effects of radioiodine in patients with differentiated thyroid cancer, there are some disadvantages due to harmful radiation to other tissues. According to the current guidelines, patients are recommended to drink lots of water and frequent voiding to reduce the amount of 131I in the body. This study was designed to assess the impact of the amount of liquid intake on reduction of the measured dose rate of radioiodine-treated patients.

MATERIALS AND METHODS

A total of 42 patients with differentiated thyroid cancer without metastasis who had undergone total thyroidectomy and had been treated with radioiodine were selected. The patients were divided into two groups according to the amount of their fluid intake which was measured during the first 48 h after 131I administration. In all patients, the dose rate was measured immediately and 48 h after iodine administration.

RESULTS

Each group included 21 patients. Dose rate ratio (the ratio of the second dose rate to the first dose rate) and dose rate difference ratio (the ratio of the difference between the two measured dose rates to the first dose rate) were calculated for each patient. Despite the significant difference in the amount of the liquid drunk, no statistically significant difference was seen between the different groups in parameters of dose-rate ratio and dose-rate difference ratio.

CONCLUSION

Higher fluid intake (>60 ml/h in our study) alone would not effectively reduce the patient's radiation dose rate at least not more than a well-hydrated state. It seems that other interfering factors in the thyroidectomized patients may also have some impacts on this physiologic process.

Evaluation of Renal Perfusion in Hyperthyroid Cats before and after Radioiodine Treatment

Background

Hyperthyroidism and chronic kidney disease (CKD) are common in elderly cats. Consequently, both diseases often occur concurrently. Furthermore, renal function is affected by thyroid status. Because changes in renal perfusion play an important role in functional renal changes in hyperthyroid cats, investigation of renal perfusion may provide novel insights.

Objectives

To evaluate renal perfusion in hyperthyroid cats with contrast‐enhanced ultrasound (CEUS).

Animals

A total of 42 hyperthyroid cats was included and evaluated before and 1 month after radioiodine treatment.

Methods

Prospective intrasubject clinical trial of contrast‐enhanced ultrasound using a commercial contrast agent (SonoVue) to evaluate renal perfusion. Time‐intensity curves were created, and perfusion parameters were calculated by off‐line software. A linear mixed model was used to examine differences between pre‐ and post‐treatment perfusion parameters.

Results

An increase in several time‐related perfusion parameters was observed after radioiodine treatment, indicating a decreased blood velocity upon resolution of the hyperthyroid state. Furthermore, a small post‐treatment decrease in peak enhancement was present in the renal medulla, suggesting a lower medullary blood volume.

Conclusions and Clinical Importance

Contrast‐enhanced ultrasound indicated a higher cortical and medullary blood velocity and higher medullary blood volume in hyperthyroid cats before radioactive treatment in comparison with 1‐month post‐treatment control.

Autoimmune Thyroiditis and Glomerulopathies

Autoimmune thyroiditis (AIT) is generally associated with hypothyroidism. It affects ~2% of the female population and 0.2% of the male population. The evidence of thyroid function- and thyroid autoantibody-unrelated microproteinuria in almost half of patients with AIT and sometimes heavy proteinuria as in the nephrotic syndrome point to a link of AIT with renal disease. The most common renal diseases observed in AIT are membranous nephropathy, membranoproliferative glomerulonephritis, minimal change disease, IgA nephropathy, focal segmental glomerulosclerosis, antineutrophil cytoplasmic autoantibody (ANCA) vasculitis, and amyloidosis. Different hypotheses have been put forward regarding the relationship between AIT and glomerulopathies, and several potential mechanisms for this association have been considered. Glomerular deposition of immunocomplexes of thyroglobulin and autoantibodies as well as the impaired immune tolerance for megalin (a thyrotropin-regulated glycoprotein expressed on thyroid cells) are the most probable mechanisms. Cross-reactivity between antigens in the setting of genetic predisposition has been considered as a potential mechanism that links the described association between ANCA vasculitis and AIT.

Thyroid dysfunction and kidney disease: An update

Thyroid hormones influence renal development, kidney hemodynamics, glomerular filtration rate and sodium and water homeostasis. Hypothyroidism and hyperthyroidism affect renal function by direct renal effects as well as systemic hemodynamic, metabolic and cardiovascular effects. Hypothyroidism has been associated with increased serum creatinine and decreased glomerular filtration rate. The reverse effects have been reported in thyrotoxicosis. Most of renal manifestations of thyroid dysfunction are reversible with treatment. Kidney disease may also cause thyroid dysfunction by several mechanisms. Nephrotic syndrome has been associated to changes in serum thyroid hormone concentrations. Different forms of glomerulonephritis and tubulointerstitial disease may be linked to thyroid derangements. A high prevalence of thyroid hormone alteration has been reported in acute kidney injury. Thyroid dysfunction is highly prevalent in chronic kidney disease patients. Subclinical hypothyroidism and low triiodothyronine syndrome are common features in patients with chronic kidney disease. Patients treated by both hemodialysis and peritoneal dialysis, and renal transplantation recipients, exhibit thyroid hormone alterations and thyroid disease with higher frequency than that found in the general population. Drugs used in the therapy of thyroid disease may lead to renal complications and, similarly, drugs used in kidney disorders may be associated to thyroid alterations. Lastly, low thyroid hormones, especially low triiodothyronine levels, in patients with chronic kidney disease have been related to a higher risk of cardiovascular disease and all-cause mortality. Interpretation of the interactions between thyroid and renal function is a challenge for clinicians involved in the treatment of patients with thyroid and kidney disease.

Albuminuria is an independent risk factor of T4 elevation in chronic kidney disease

This study was to explore the association between thyroid dysfunction and albuminuria. 581 cases with chronic kidney disease (CKD) were included in this study. The clinical characteristics consisted of sex, age, serum creatinine, urinary albumin-to-creatinine ratio (ACR), thyroid function were recorded. Estimated glomerular filtration rate (eGFR) was calculated by CKD-EPI four-level race equation. Prevalence of different thyroid diseases was calculated by chi-square test. Levels of thyroid hormone were compared among different albuminuria groups by Kruskal-Wallis test. Spearman's correlation was used to assess the association between albuminuria and thyroid hormone. Our study showed that total T4 and free T4 were significantly different among ACR < 30 mg/g, 30-300 mg/g and >300 mg/g (P < 0.001 and =0.007, respectively). Positive correlation between T4 (total T4 and free T4) and albuminuria was evaluated by correlation analysis (P = 0.001 and <0.001, respectively). Albuminuria was an independent influence factor of T4 after adjustment for age, sex, serum creatinine, albumin, hs-CRP, smoking status, systolic blood pressure, diabetes mellitus, medication use for diabetes mellitus, eGFR, LDL-cholesterol, triglycerides, hypertension, and medication use for hypercholesterinemia. In conclusion, T4 was positively correlated with albuminuria, and it was completely not consistent with our anticipation. Further study is needed to elucidate the causation association between albuminuria and T4.

Proteinuria in Apparently Healthy Elderly Dogs: Persistency and Comparison Between Free Catch and Cystocentesis Urine

BACKGROUND

Up to 25% of elderly humans have proteinuria, often associated with underlying lesions. Data concerning the presence of proteinuria in elderly dogs is scarce.

OBJECTIVES

To describe the presence and persistence of proteinuria and to compare urinary protein : creatinine ratio (UPC) between free catch and cystocentesis urine samples in apparently healthy elderly dogs.

ANIMALS

Hundred apparently healthy elderly dogs.

METHODS

Prospective study. Owners of 100 elderly dogs were asked to collect 2 free catch urine samples. Dogs were considered healthy based on owner's perception and an age chart, based on ideal bodyweight, was used to define dogs as senior or geriatric. UPC of urine collected by free catch and cystocentesis were compared. Overt proteinuria and borderline proteinuria were defined as UPC >0.5 and between 0.2 and 0.5, respectively, if examination of sediment did not explain proteinuria. Proteinuria was considered persistent if present at both sampling times.

RESULTS

At baseline, 71 owners succeeded in collecting urine. Eleven percent of dogs had overt proteinuria, 14% were borderline proteinuric, and 75% nonproteinuric. Thirty-seven repeated urine samples, with a median time interval of 31 days (range 10-90), were available. Nineteen percent of dogs had a persistently increased UPC (>0.2), with persistent overt proteinuria present in 8%. A strong correlation (ρ = 0.88) was found between UPC of urine collected by free catch and cystocentesis.

CONCLUSIONS AND CLINICAL IMPORTANCE

As 19% of study dogs had persistent proteinuria, our findings emphasize that measurement of proteinuria should be part of geriatric health screening. For UPC in dogs, free catch urine provides a good alternative to cystocentesis.

Serum and urinary cystatin C in cats with feline immunodeficiency virus infection and cats with hyperthyroidism

OBJECTIVES

The objective of this study was to investigate serum cystatin C (sCysC) and urinary cystatin C (uCysC) in cats with hyperthyroidism and cats with feline immunodeficiency virus (FIV).

METHODS

Thirty cats with FIV, 26 hyperthyroid cats and 28 healthy cats were included. sCysC and uCysC:creatinine (uCysC/uCr) ratio were measured with a human particle-enhanced nephelometric immunoassay, previously validated for feline CysC measurement. Routine renal variables (serum creatinine [sCr], urine specific gravity, urinary protein:creatinine ratio [UPC]) were also measured in the three groups.

RESULTS

Cats with hyperthyroidism had significantly higher sCysC and higher uCysC/uCr ratio, lower sCr and a higher UPC than healthy cats. Cats with FIV infection did not show a significantly higher sCysC concentration but had a significantly higher sCr and UPC than healthy cats. uCysC could be detected in only four of them.

CONCLUSIONS AND RELEVANCE

This study demonstrated that sCysC is increased in cats with hyperthyroidism, in contrast with sCr, but not in cats with FIV. Many hyperthyroid cats, but only four cats with FIV, had an elevated uCysC/uCr ratio. Further studies may reveal if uCysC might be a valuable marker for tubular dysfunction in cats.

THYROID FUNCTION IN DOGS WITH VISCERAL LEISHMANIASIS

Resumo Vários fatores extratireoidianos como idade, raça, doenças concomitantes e fármacos podem influenciar na função e no diagnóstico do hipotireoidismo em cães. As alterações nas concentrações dos hormônios tireoidianos decorrentes de doenças não tireoidianas é denominada de síndrome do eutireoideo doente. O objetivo deste estudo foi avaliar a influência da leishmaniose visceral na função da tireoide em cães sem sinais de hipotireoidismo, com ou sem azotemia. Os animais positivos para leishmaniose foram divididos em seis grupos (albumina nornal ou diminuída, creatinina normal ou elevada, uréia normal ou elevada) e foi avaliado o efeito nesses grupos das concentrações séricas do hormônio estimulante da tireoide (TSH), tiroxina total (TT4) e da tiroxina livre (FT4). Os cães positivos para leishmaniose, pelo teste de ELISA, apresentaram concentrações séricas de TSH mais elevadas do que os animais soronegativos, enquanto que as concentrações de TT4 e FT4 em cães com leishmaniose foram menores (P <0,01) quando comparadas com as dos cães saudáveis. No entanto, os resultados estavam no intervalo dos valores para os animais eutireoideos. Nos cães seropositivos para leishmaniose, a TT4 apresentou diferença estatística significativa (P <0,04) no grupo com hipoalbuminemia em relação ao grupo com normoalbuminemia, respectivamente, 1,01ug/dL e 1,4ug/dL. Concluiu-se que os cães positivos para a leishmaniose visceral não desenvolveram síndrome do doente eutireóide, embora as concentrações de TT4 e a FT4 estivessem reduzida e de TSH elevada em relação aos cães sem leishmaniose.

ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease

PRACTICAL RELEVANCE

Chronic kidney disease (CKD) is one of the most commonly diagnosed diseases in older cats. In most cats, CKD is also a progressive disease and can be accompanied by a wide range of clinical and clinicopathological changes. These ISFM Consensus Guidelines have been developed by an independent panel of clinicians and academics to provide practical advice on the diagnosis and management of this complex disease.

CLINICAL CHALLENGES

Although CKD is a common clinical problem in cats, the manifestations of disease vary between individuals. Thus there is a need for careful and repeat evaluation of cats with CKD and adjustment of therapy according to individual needs. In addition to addressing problems arising from CKD and improving quality of life (QoL) for the patient, therapy may also target slowing the underlying progression of disease and hence prolonging life. While maintaining QoL is of paramount importance in our patients, this can be challenging when multiple therapies are indicated. In some cases it is necessary to prioritise therapy, given an understanding of what is likely to most benefit the individual patient.

EVIDENCE BASE

In preparing these Guidelines, the Panel has carefully reviewed the existing published literature, and has also graded the quality of evidence for different interventions to help to provide practical recommendations on the therapeutic options for feline CKD. This is a field of veterinary medicine that has benefited from some excellent published clinical research and further research findings will undoubtedly modify the recommendations contained in these Guidelines in the future.

Chronic Kidney Disease in Aged Cats: Clinical Features, Morphology, and Proposed Pathogeneses

Chronic kidney disease (CKD) is the most common metabolic disease of domesticated cats, with most affected cats being geriatric (>12 years of age). The prevalence of CKD in cats exceeds that observed in dogs, and the frequency of the diagnosis of CKD in cats has increased in recent decades. Typical histologic features include interstitial inflammation, tubular atrophy, and fibrosis with secondary glomerulosclerosis. In contrast to people and dogs, primary glomerulopathies with marked proteinuria are remarkably rare findings in cats. Although a variety of primary renal diseases have been implicated, the disease is idiopathic in most cats. Tubulointerstitial changes, including fibrosis, are present in the early stages of feline CKD and become more severe in advanced disease. A variety of factors-including aging, ischemia, comorbid conditions, phosphorus overload, and routine vaccinations-have been implicated as factors that could contribute to the initiation of this disease in affected cats. Factors that are related to progression of established CKD, which occurs in some but not all cats, include dietary phosphorus intake, magnitude of proteinuria, and anemia. Renal fibrosis, a common histologic feature of aged feline kidneys, interferes with the normal relationship between peritubular capillaries and renal tubules. Experimentally, renal ischemia results in morphologic changes similar to those observed in spontaneous CKD. Renal hypoxia, perhaps episodic, may play a role in the initiation and progression of this disease.

Thyroid function modifies the association between ratio of triglyceride to high-density lipoprotein cholesterol and renal function: a multicenter cross-sectional study

Hypothyroidism was confirmed to be associated with both dyslipidemia and renal dysfunction. However, the impact of thyroid function on the relationship between serum lipid levels and renal function has never been given sufficient attention. In this large-scale multicenter cross-sectional study, the ratio of triglyceride to high-density lipoprotein cholesterol (TG/HDL) and the prevalence of hypothyroidism in CKD subjects were significantly higher than those in non-CKD ones (P < 0.001). After adjustment for potential confounding factors, TG/HDL was shown to be significantly associated with serum Cr levels (β = 0.551; 95%CI, 0.394–0.708), and eGFR (β = −0.481; 95%CI, −0.731–−0.230). The risk for CKD was significantly increased as TG/HDL ratio was elevated (adjusted odds ratio = 1.20; 95%CI, 1.11–1.27). These significant associations were found among subjects with euthyroidism and hypothyroidism rather than hyperthyroidism. Furthermore, the associations between TG/HDL and Cr or CKD status were significantly greater in hypothyroidism than those in euthyroidism (P < 0.05). These results suggested that elevated TG/HDL ratio was associated with renal dysfunction; it exhibited a significantly stronger association with Cr and CKD in hypothyroidism than in euthyroidism. Therefore, more attention should be paid on lipid profile to prevent or delay the occurrence and progression of renal dysfunction, especially for those with hypothyroidism.

Effect of Feeding an Iodine-Restricted Diet in Cats with Spontaneous Hyperthyroidism

BACKGROUND

Exclusive feeding of an iodine-restricted diet has been proposed as a method for controlling clinical manifestations of hyperthyroidism in hyperthyroid cats.

OBJECTIVES

To determine the effect of feeding an iodine-restricted diet on TT4 concentrations and clinical signs in cats with spontaneous hyperthyroidism.

ANIMALS

Forty-nine client-owned cats with spontaneous hyperthyroidism.

METHODS

Retrospective case series. Hyperthyroid cats were exclusively fed a commercially available iodine-restricted diet. Clinical response was assessed by change in weight and heart rate and serum TT4, blood urea nitrogen (BUN), and creatinine concentrations at various times during dietary management (21-60 days, 60-180 days).

RESULTS

Serum TT4 normalized in 20/48 cats (42%) and 39/47 cats (83%) at 21-60 days and 61-180 days, respectively. Cats in which the TT4 concentrations were still above reference range at 21-60 days had a significantly higher starting TT4 than those that normalized their TT4 levels during the same time period (P = .038). Body weight did not significantly increase (P = .34) nor heart rate decrease (P = .64) during the study. There was a significant decrease in serum creatinine (P = .028). Cats in the low reference range for serum TT4 concentrations did not have a significant increase in body weight (P = .41) nor creatinine (P = .54) when compared to those with high reference range.

CONCLUSIONS AND CLINICAL IMPORTANCE

Restricted-iodine diets were effective at maintaining serum TT4 concentrations within reference ranges for a majority of cats with spontaneous hyperthyroidism over 1 year, although not all clinical signs of hyperthyroidism improved.

Low T3 syndrome in canine babesiosis associated with increased serum IL-6 concentration and azotaemia

Low triiodothyronine (T3) syndrome, also named euthyroid sick syndrome or non-thyroidal illness syndrome, has been recognized in canine babesiosis caused by Babesia rossi, where it manifested by lowering of the serum thyrotropin (TSH), total thyroxin (TT4) and free thyroxin (FT4) concentrations. This syndrome has also been observed in critical diseases in humans and animals, and the severity of the disease is considered an important factor in lowering of thyroid hormone concentrations. Interleukin-6 (IL-6) plays a role in the development of low T3 syndrome by causing a decrease in deiodinases 1 and 2 activity and increased activity of deiodinase 3, enzymes involved in the conversion of thyroxin (T4) to T3. The purpose of this study was to compare the concentrations of serum thyroid hormones and TSH between healthy dogs and dogs with babesiosis, and to determine correlations between serum IL-6 concentration and serum total T3 (TT3), TT4, FT4, and TSH concentrations, and the level of azotaemia in dogs with babesiosis. The concentrations of IL-6, TT3, TT4, FT4, TSH, urea and creatinine were determined in 13 dogs with canine babesiosis caused by Babesia canis and in 10 healthy dogs. The results of this study showed decreases in TT3, TT4, FT4, and TSH and increases in IL-6, urea and creatinine concentrations in affected dogs in comparison to healthy dogs. The concentration of IL-6 was negatively correlated with TT3 and TSH concentrations and the TT3 concentration was negatively correlated with serum urea and creatinine concentrations. This study showed low T3 syndrome in canine babesiosis, which was confirmed by the determination of the T3 concentration, and demonstrates that in canine babesiosis the T3 concentration is associated with IL-6 concentration.

Congenital hypothyroidism and concurrent renal insufficiency in a kitten

A 3-month-old male domestic short-hair kitten was presented with chronic constipation and disproportionate dwarfism. Radiographs of the long bones and spine revealed delayed epiphyseal ossification and epiphyseal dysgenesis. Diagnosis of congenital primary hypothyroidism was confirmed by low serum total thyroxine and high thyroid stimulating hormone concentrations. Appropriate supplementation of levothyroxine was instituted. The kitten subsequently developed mild renal azotaemia and renal proteinuria, possibly as a consequence of treatment or an unmasked congenital renal developmental abnormality. Early recognition, diagnosis and treatment are vital as alleviation of clinical signs may depend on the cat's age at the time of diagnosis.

Cystatin C: a new renal marker and its potential use in small animal medicine

The occurrence of chronic kidney disease is underestimated in both human and veterinary medicine. Glomerular filtration rate (GFR) is considered the gold standard for evaluating kidney function. However, GFR assessment is time-consuming and labor-intensive and therefore not routinely used in practice. The commonly used indirect GFR markers, serum creatinine (sCr) and urea, are not sufficiently sensitive or specific to detect early renal dysfunction. Serum cystatin C (sCysC), a proteinase inhibitor, has most of the properties required for an endogenous GFR marker. In human medicine, numerous studies have evaluated its potential use as a GFR marker in several populations. In veterinary medicine, this marker is gaining interest. The measurement is easy, which makes it an interesting parameter for clinical use. This review summarizes current knowledge about cystatin C (CysC) in humans, dogs, and cats, including its history, assays, relationship with GFR, and biological and clinical variations in both human and veterinary medicine.

Salt-losing nephropathy in hypothyroidism

A 35-year-old man presented with recurrent lower extremity weakness associated with polyuria later progressing to generalised weakness with difficulty in breathing. The patient was hypotensive and dry, with normal thyroid and chest examination, weak lower extremity and carpopedal spasm. Workup revealed hypokalaemia, hyponatraemia, hypocalcaemia, hypomagnesaemia, hypochloraemia and hypophosphataemia. Arterial blood gas showed respiratory alkalosis with good oxygenation. Twenty-four-hour urine collection showed normal volume with electrolyte wasting. Thyroid function test revealed overt hypothyroidism with negative antithyroid peroxidase. The patient was well after treatment with levothyroxine, volume and electrolyte replacement and was discharged. Thyroid hormones are related to the expression of the Na-K-ATPase, Na-Pi cotransporter, Mg-ATPase and Na-Ca exchanger pumps in the renal tubules. Sodium, potassium, phosphate, calcium, magnesium and water losses result from decreased expression of these pumps.

The thyroid and the kidney: a complex interplay in health and disease

Thyroid hormones may directly affect the kidney and altered kidney function may also contribute to thyroid disorders. The renal manifestations of thyroid disorders are based on hemodynamic alterations or/and to direct effects of thyroid hormones. The renin-angiotensin system plays a crucial role in the cross-talk between the thyroid and the kidney. Hypothyroidism may be accompanied by an increase of serum creatinine and reduction of glomerular filtration rate (GFR), whereas hyperthyroidism may increase GFR. Treatment of thyroid disorders may lead to normalization of GFR. Primary and subclinical hypothyroidism and low triiodothyronine (T3) syndrome are common features in patients with chronic kidney disease (CKD). In addition low levels of thyroid hormones may predict a higher risk of cardiovascular and overall mortality in patients with end-stage renal disease. The causal nature of this correlation remains uncertain. In this review, special emphasis is given to the thyroid pathophysiology, its impact on kidney function and CKD and the interpretation of laboratorial findings of thyroid dysfunction in CKD.

The impact of low triiodothyronine levels on mortality is mediated by malnutrition and cardiac dysfunction in incident hemodialysis patients

OBJECTIVE

Little is known about the impact of low triiodothyronine (T3) levels on mortality in end-stage renal disease (ESRD) patients starting hemodialysis (HD) and whether this impact is mediated by malnutrition, inflammation, or cardiac dysfunction.

DESIGN AND METHODS

A prospective cohort of 471 incident HD patients from 36 dialysis centers within the Clinical Research Center for ESRD in Korea was selected for this study. Based on the median value of T3, patients were divided into 'higher' and 'lower' groups, and all-cause and cardiovascular (CV) mortality rates were compared. In addition, associations between T3 levels and various nutritional, inflammatory, and echocardiographic parameters were determined.

RESULTS

Compared with those in the 'higher' T3 group, albumin, cholesterol, and triglyceride levels, lean body mass estimated by creatinine kinetics (LBM-Cr), and normalized protein catabolic rate (nPCR) were significantly lower in patients with 'lower' T3 levels. The 'lower' T3 group also had a higher left ventricular mass index (LVMI) and a lower ejection fraction (EF). Furthermore, correlation analysis revealed significant associations between T3 levels and nutritional and echocardiographic parameters. All-cause and CV mortality rates were significantly higher in patients with 'lower' T3 levels than in the 'higher' T3 group (113.4 vs 18.2 events per 1000 patient-years, P<0.001, and 49.8 vs 9.1 events per 1000 patient-years, P=0.001, respectively). The Kaplan-Meier analysis also showed significantly worse cumulative survival rates in the 'lower' T3 group (P<0.001). In the Cox regression analysis, low T3 was an independent predictor of all-cause mortality even after adjusting for traditional risk factors (hazard ratio=3.76, P=0.021). However, the significant impact of low T3 on all-cause mortality disappeared when LBM-Cr, nPCR, LVMI, or EF were incorporated into the models.

CONCLUSION

Low T3 has an impact on all-cause mortality in incident HD patients, partly via malnutrition and cardiac dysfunction.

Feline CKD: Pathophysiology and risk factors--what do we know?

PRACTICAL RELEVANCE

Chronic kidney disease (CKD) is one of the most frequently encountered disorders in cats, having increased in prevalence in recent decades. Although the underlying cause is rarely identified, the common final outcome of feline CKD is tubulointerstitial fibrosis. Knowledge of CKD pathophysiology is necessary for optimal individualised patient management, especially with regard to diagnosis and treatment of extrarenal complications.

PATIENT GROUP

CKD is most common in senior and geriatric cats, but should be considered in any feline patient with ureterolithiasis, hyperthyroidism, retrovirus infection, systemic hypertension, cardiovascular disease or urinary tract infection.

EVIDENCE BASE

Most of our knowledge of the pathogenesis of CKD is extrapolated from human nephrology and experimental animal studies. There is, therefore, a need for further studies in cats. The prevalence of clinical signs in feline CKD is well documented. Several concurrent diseases associated with CKD have also been reported in cats, especially in the geriatric population, but there is no or only limited published evidence demonstrating a cause-and-effect relationship between most of these conditions and CKD. Studies performed over the past 15 years have nevertheless allowed identification of major risk factors (proteinuria, plasma phosphate and plasma creatinine) influencing the progression of feline CKD.

CLINICAL CHALLENGES

Clinical signs occur in the late stages of renal disease, so populations at higher risk of CKD should be screened routinely. CKD-associated complications (systemic hypertension, secondary renal hyperparathyroidism, hypokalaemia, anaemia, metabolic acidosis) must not be overlooked as they may affect the progression of disease. Disease progression is itself unpredictable and renal function may remain stable for extended periods. Most cats with early CKD do not progress to end-stage CKD before they die.

AUDIENCE

General practitioners play a major role in screening feline patients at risk of development or progression of CKD.