Risk factors for feline hyperthyroidism in the UK

Serum metabolome analysis in hyperthyroid cats before and after radioactive iodine therapy

Hyperthyroidism is the most common feline endocrinopathy. In hyperthyroid humans, untargeted metabolomic analysis identified persistent metabolic derangements despite achieving a euthyroid state. Therefore, we sought to define the metabolome of hyperthyroid cats and identify ongoing metabolic changes after treatment. We prospectively compared privately-owned hyperthyroid cats (n = 7) admitted for radioactive iodine (I-131) treatment and euthyroid privately-owned control (CON) cats (n = 12). Serum samples were collected before (T0), 1-month (T1), and three months after (T3) I-131 therapy for untargeted metabolomic analysis by MS/MS. Hyperthyroid cats (T0) had a distinct metabolic signature with 277 significantly different metabolites than controls (70 increased, 207 decreased). After treatment, 66 (T1 vs. CON) and 64 (T3 vs. CON) metabolite differences persisted. Clustering and data reduction analysis revealed separate clustering of hyperthyroid (T0) and CON cats with intermediate phenotypes after treatment (T1 & T3). Mevalonate/mevalonolactone and creatine phosphate were candidate biomarkers with excellent discrimination between hyperthyroid and healthy cats. We found several metabolic derangements (e.g., decreased carnitine and α-tocopherol) do not entirely resolve after achieving a euthyroid state after treating hyperthyroid cats with I-131. Further investigation is warranted to determine diagnostic and therapeutic implications for candidate biomarkers and persistent metabolic abnormalities.

Endocrine-Disrupting Chemicals and Their Effects in Pet Dogs and Cats: An Overview

Over the past few decades, several pollutants classified as environmental endocrine-disrupting chemicals (EDCs) have become a matter of significant public health concern. Companion animals play a major role in human society, and pet ownership is substantially increasing worldwide. These intimate human-pet relationships imply sharing much of the same environment, thus including exposure to similar levels of EDCs in daily routine. Here, we review the current knowledge on the sources and routes of exposure to EDCs in domestic indoor and outdoor environments and discuss whether endocrine disruption is a health concern in pets. We summarize the phenomenon of endocrine disruption, providing examples of EDCs with a known impact on dog and cat health. Then, we propose an overview of the literature on the adverse effects of EDCs in domestic pets, with a special focus on the health of reproductive and thyroid systems. Finally, we explore the potential role of companion animals as unintentional sentinels of environmental exposure to EDCs and the implications for public health risk assessment in a "shared risk" scenario. Overall, this review supports the need for an integrated approach considering humans, animals, and the environment as a whole for a comprehensive assessment of the impact of EDCs on human and animal health.

2022 AAFP/ISFM Cat Friendly Veterinary Interaction Guidelines: Approach and Handling Techniques

PRACTICAL RELEVANCE

The '2022 AAFP/ISFM Cat Friendly Veterinary Interaction Guidelines: Approach and Handling Techniques' (hereafter the 'Cat Friendly Veterinary Interaction Guidelines') support veterinary professionals with feline interactions and handling to reduce the impact of fear and other protective (negative) emotions, in so doing enhancing feline welfare and In implementing these Guidelines, team satisfaction and cat caregiver confidence in the veterinary team will increase as the result of efficient examinations, better experience, more reliable diagnostic testing and improved feline wellbeing. Veterinary professionals will learn the importance of understanding and appropriately responding to the current emotional state of the cat and tailoring each visit to the individual.

CLINICAL CHALLENGES

Cats have evolved with emotions and behaviors that are necessary for their survival as both a predator and prey species. A clinical setting and the required examinations and procedures to meet their physical health needs can result in behavioral responses to protective emotions. Cat friendly interactions require understanding, interpreting and appropriately responding to cats' emotional states and giving them a perceived sense of control while performing the required assessment.

EVIDENCE BASE

These Guidelines have been created by a Task Force of experts convened by the American Association of Feline Practitioners and the International Society of Feline Medicine, based on an extensive literature review and, where evidence is lacking, the authors' experience.

ENDORSEMENTS

These Guidelines have been endorsed by a number of groups and organizations, as detailed on page 1127 and at catvets.com/interactions and icatcare.org/cat-friendly-guidelines.

Estimating short and longer-term exposure of domestic cats to dietary iodine fluctuation

Hyperthyroidism is a common endocrinopathy of domestic felines. In humans, toxic nodular goitre is pathophysiologically similar to feline hyperthyroidism and can be caused by chronically low or fluctuating dietary iodine intake. The aetiopathogenesis of feline hyperthyroidism is not known, but chronically low or fluctuating dietary iodine intake is likely common. This study assessed habitual iodine intake in domestic cats by: (1) conducting a dietary survey involving 361 owners of 549 cats, (2) analysing iodine content of 119 cat feeds, 38 urine and 64 hair samples and (3) assessing variation in iodine content of eight cat feeds over 4–6 different batches. Owners varied their cats feed regularly, usually on a day-to-day basis and often between wet and dry feeds with differing flavours. The majority (78%; 93 of 119) feeds for cats were within the guideline range for iodine. Of the 22% (n = 26 feeds) that were not compliant, the majority (n = 23) were below the nutritional minimum value with most (n = 16) being dry kibble. Iodine content of feeds did not vary considerably between types of feed or feed packaging, but variation between different batches of the same feed was 14–31%. Hence, urine iodine in cats also varied markedly. Cats being treated for hyperthyroidism had lower hair iodine. In conclusion, a survey assessing how domestic cats are fed, together with an analysis of commercial cat feeds suggests that domestic cats are likely to experience chronically low or fluctuating dietary iodine intake. The latter is supported by wide variation in urine iodine content.

Aging in Cats: Owner Observations and Clinical Finding in 206 Mature Cats at Enrolment to the Cat Prospective Aging and Welfare Study

Two hundred and six cats, aged between 7 and 10 years, from the North-west of the UK, were enrolled in a cat aging and welfare study to determine the frequency of age-related conditions and associations with husbandry, owner observations of physical appearance, activity and behavior. This is the largest study to date of mature cats that includes data from an owner questionnaire and clinical examinations. At enrolment, owners frequently reported physical changes (53%), behavioral changes (47%), changes to eating patterns (41%), and activity changes (40%) in their mature cats. On physical examination, 45% cats were in overweight condition and 12% were obese. A heart murmur was detected in 29% cats, whilst indirect systolic blood pressure (SBP) was >160 mmHg in 5% cats. Dental disease was present in 54% cats and was associated with a matted hair coat (P = 0.01), increased sleeping (P = 0.02), absence of gray hairs (P = 0.03), and increased irritability to other pets (P = 0.04). Abnormalities were evident in 58% of cats that allowed an orthopedic examination (OE) to be performed. These cats were older than cats with a normal OE (P = 0.01), and abnormal OE findings were associated with a matted coat (P = 0.03) and increased grooming (P = 0.04). Aazotaemia was present in 10% cats, and this was associated with cats being observed to “sniff their food and then walk away” (P = 0.04). Hyperthyroidism was diagnosed in 3% cats, who were older (P = 0.02), had a leaner BCS (P = 0.02) and lesser blood creatinine concentrations (P = 0.01). Hyperthyroid cats were also more likely to have increased liver enzyme activity and increased SBP (P = <0.001) compared with non-hyperthyroid cats. Of the 176 cats where all clinical assessments were conducted, only 12% had no evidence of any disease. Clinical abnormalities are commonly identified when thorough, clinical assessments are performed in mature pet cats visiting primary care practice.

Serum concentration of bisphenol A in elderly cats and its association with clinicopathological findings

OBJECTIVES

Bisphenol A (BPA) has been mentioned as a possible factor contributing to feline hyperthyroidism. Nevertheless, there are no previous studies reporting on the concentration of BPA in feline serum and its association with thyroid function. The objectives of this study were to measure serum BPA concentration in cats aged ⩾7 years, considered as healthy by their owners, and to compare the results with clinicopathological findings.

METHODS

Sixty-nine cats aged ⩾7 years considered as healthy by their owners were enrolled in the study. The concentration of BPA in feline serum was measured using liquid chromatography-tandem mass spectrometry. In all cats, signalment, living environment, diet history, and the results of haematological and biochemical analysis, including thyroxine levels, were available.

RESULTS

The mean serum BPA concentration in feline serum was 1.06 ± 0.908 ng/ml. Significant correlation was found between BPA concentration and haemoglobin (r = 0.3397; P = 0.0043), haematocrit (r = 0.3245; P = 0.0065) and the number of red blood cells (r = 0.2916; P = 0.0151), concentration of total protein (r = 0.2383; P = 0.0486), concentration of calcium (r = 0.3915; P = 0.0009) and level of bilirubin (r = 0.3848; P = 0.0011). No other significant correlations were found. Significant differences (P <0.01) were found between mature (1.28 ± 0.994 ng/ml) and geriatric cats (0.420 ± 0.240 ng/ml), between strictly indoor cats (1.27 ± 0.992 ng/ml) and cats with outdoor access (0.660 ± 0.529 ng/ml), and between cats fed canned food (1.23 ± 0.935 ng/ml) and cats fed non-canned food (0.774 ± 0.795 ng/ml).

CONCLUSIONS AND RELEVANCE

Measurable serum BPA levels were found in all examined samples. The age of the cats was revealed as a significant factor affecting BPA concentration and mature cats had the highest levels. A significantly higher concentration of BPA was found in cats living strictly indoors and in cats fed canned food. No association was found between BPA and thyroid function. Further studies are needed that focus on hyperthyroid cats for better evaluation of this relationship.

Effects of PCB exposure on serum thyroid hormone levels in dogs and cats

Polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs) might disrupt thyroid function. However, there is no clear evidence of PCB exposure disrupting thyroid hormone (TH) homeostasis in dogs and cats. The present study conducted in vivo experiments to evaluate the effects of a mixture of 12 PCB congeners (CB18, 28, 70, 77, 99, 101, 118, 138, 153, 180, 187 and 202, each congener 0.5 mg/kg BW, i.p. administration) on serum TH levels in male dogs (Canis lupus familiaris) and male cats (Felis silvestris catus). In PCB-exposed dogs, the time courses of higher-chlorinated PCBs and L-thyroxine (T4)-like OH-PCBs (4-OH-CB107 and 4-OH-CB202) concentrations were unchanged or tended to increase, whereas those of lower-chlorinated PCBs and OH-PCBs tended to decrease after 24 h. In PCB-exposed cats, concentrations of PCBs increased until 6 h and then remained unchanged. The levels of lower-chlorinated OH-PCBs including 4'-OH-CB18 increased until 96 h and then decreased. In PCB-exposed dogs, free T4 concentrations were higher than those in the control group at 48 and 96 h after PCB administration and positively correlated with the levels of T4-like OH-PCBs, suggesting competitive binding of T4 and T4-like OH-PCBs to a TH transporter, transthyretin. Serum levels of total T4 and total 3,3',5-triiodo-L-thyronine (T3) in PCB-exposed dogs were lower than in the control group at 24 and 48 h and negatively correlated with PCB concentrations, implying that PCB exposure enhanced TH excretion by increasing TH uptake and TH conjugation enzyme activities in the dog liver. In contrast, no obvious changes in TH levels were observed in PCB-exposed cats. This could be explained by the lower levels of T4-like OH-PCBs and lower hepatic conjugation enzyme activities in cats compared with dogs. Different effects on serum TH levels in PCB-exposed dogs and cats are likely to be attributable to species-specific PCB and TH metabolism.

Are persistent organic pollutants important in the etiology of feline hyperthyroidism? A review

Feline hyperthyroidism is a rather new disease, first reported from the North American east coast in 1979. The prevalence is increasing, especially in older cats, and hyperthyroidism is now reported worldwide as the most common feline endocrinopathy. Several studies have been performed trying to identify important etiological factors such as exposure to persistent organic pollutants, and especially brominated flame retardants, have been suggested to be of importance for the development of the disease. Recent studies have shown higher concentrations of these contaminants in serum of hyperthyroid cats in comparison to cats with normal thyroid status. However, other still unknown factors are most probably of importance for the development of this disease.

Silicone Pet Tags Associate Tris(1,3-dichloro-2-isopropyl) Phosphate Exposures with Feline Hyperthyroidism

Feline hyperthyroidism is the most commonly diagnosed endocrine-related disease among senior and geriatric housecats, but the causes remain unknown. Exposure to endocrine-disrupting compounds with thyroid targets, such as flame retardants (FRs), may contribute to disease development. Silicone passive sampling devices, or pet tags, quantitatively assessed the bioavailable FR exposures of 78 cats (≥7 y) in New York and Oregon using gas chromatography-mass spectrometry. Pet tags were analyzed for 36 polybrominated diphenyl ethers, six organophosphate esters (OPEs), and two alternative brominated FRs. In nonhyperthyroid cats, serum free thyroxine (fT4), total T4 (TT4), total triiodothyronine, and thyroid-stimulating hormone concentrations were compared with FR concentrations. Tris(1,3-dichloro-2-isopropyl) phosphate (TDCIPP) concentrations were higher in hyperthyroid pet tags in comparison to nonhyperthyroid pet tags (adjusted odds ratio, p < 0.07; Mantel-Cox, p < 0.02). Higher TDCIPP concentrations were associated with air freshener use in comparison to no use (p < 0.01), residences built since 2005 compared to those pre-1989 (p < 0.002), and cats preferring to spend time on upholstered furniture in comparison to no preference (p < 0.05). Higher TDCIPP concentrations were associated with higher fT4 and TT4 concentrations (p < 0.05). This study provides proof-of-concept data for the use of silicone pet tags with companion animals and further indicates that bioavailable TDCIPP exposures are associated with feline hyperthyroidism.

Inhibitory effect of Bisphenol A on in vitro feline uterine contractions

Bisphenol A (BPA) is an environmental pollutant used as a plasticizer in the manufacture of many plastic products, such as packaging, containers, and water and beverage bottles. There are deleterious effects of BPA on metabolic, endocrine, nervous, and reproductive systems. This is the first study in which there was investigation of the in vitro effect of BPA on the spontaneous contractions of the cat uterus. The tubal uterine segments (1 cm) collected from queens in estrus were suspended in an isolated organ bath. Following tissue stabilization, spontaneous contractions were recorded for 10 min to constitute the control group. The effects of the solvent (alcohol) and BPA at different concentrations (1, 10, and 100 μM) on uterine contractions were subsequently evaluated at 10 min intervals in terms of frequency and mean amplitude variables. The ethanol vehicle did not alter the uterine contractions compared to the control group. All concentrations of BPA used in the study resulted in a reduction (P < 0.05) in amplitude of uterine contractions in a dose-dependent manner, while only the largest dose of BPA decreased the frequency of contractions (P < 0.05). In reproductive physiology, regular uterine contractions facilitate successful fertilization, migration, implantation, and maintenance of pregnancy, as well as fetus expulsion. The results of this study indicate BPA has an inhibitory effect on spontaneous contractions of the cat uterus. It is proposed that this suppressive effect of BPA on uterine contractions might lead to queen infertility.

Prevalence and risk factors for hyperthyroidism in Irish cats from the greater Dublin area

Background

Hyperthyroidism is common in older cats. Prevalence varies geographically, but is anecdotally considered low in Ireland. The aim of this study was to document prevalence of hyperthyroidism in older cats in the greater Dublin area of Ireland and to assess environmental and clinical associations for development and identification of the disease.

Methods

Primary-care veterinary practices were requested to select cats aged 10 years or older where blood sampling was being performed for health screening or clinical investigations. Surplus serum/plasma samples were submitted to University College Dublin Diagnostic Endocrine Laboratory for total thyroxine (T₄) measurement. Cats were classified as hyperthyroid, equivocal or euthyroid based on a total T₄ concentration (reference interval, 15-60 nmol/L), of >60 nmol/L, 30-60 nmol/L or <30 nmol/L, respectively. Simultaneous free T₄ or repeat (after 4-6 weeks) total T₄ measurement was recommended in all equivocal cases. Animals receiving treatment for hyperthyroidism were excluded. A questionnaire completed by the client and veterinarian detailing historical and physical information was also required. Associations between categorical variables were analysed by Chi-square or Fisher's exact test and odds ratio (OR) calculated. A P value of <0.05 was considered statistically significant.

Results

Samples were submitted from 507 cats including 107 (21.1%) hyperthyroid, 54 (10.6%) equivocal and 346 (68.2%) euthyroid. The presence of goitre (P < 0.0001), tachypnoea (P = 0.0378), tachycardia (P = 0.002), polyphagia (P = 0.0003) and weight loss (P < 0.0001) were significantly associated with hyperthyroidism. Cats with goitre were more likely to be diagnosed as hyperthyroid [OR 2.85, (95% CI 1.75-4.62] compared to those without. However, goitre was only palpated in 40 of 102 (39.2%) hyperthyroid cats. Increasing age was the only significant (P < 0.002) risk factor for development of hyperthyroidism. A relationship between hyperthyroidism and sex, breed, lifestyle, parasite control, vaccination status or feeding habits was not identified.

Conclusions

Hyperthyroidism is not uncommon in Irish cats. Age was the only significant risk factor for its development. The high proportion of hyperthyroid cats without palpable goitre (> 60%) may reflect failure to detect goitre and account for the perceived low prevalence of this condition in Ireland.

Prävalenz und Risikofaktoren der felinen Hyperthyreose in einer Klinik population in Süddeutschland

Ziel: Die feline Hyperthyreose ist eine häufige Endokrinopathie bei älte ren Katzen. In früheren Studien wurden unausgewogene Ernährung, Schilddrüsen-Disruptoren, hohes Alter sowie fehlende Reinrassigkeit als Risikofaktoren diskutiert, ein endgültiger Auslöser bleibt jedoch unbekannt. Die Ziele dieser prospektiven Studie waren a) die Berech nung der Klinikprävalenz in einer Katzenpopulation in Süddeutschland, b) die Feststellung, wie häufig die Diagnose nach dem klini schem Verdacht bestätigt wurde und c) die Auswertung mutmaßlicher in- und extrinsischer Risikofaktoren anhand des Signalements der Katzen und eines Fragebogens. Methoden: Gesamt-Thyroxin (T4) wurde im Serum von 495 Katzen ≥ 8 Jahre gemessen und die Prävalenz mit einem 95%-Konfidenzintervall (95%-KI) berechnet. Abhängigkeiten zwischen Signalement und Hyperthyreose wurden durch den Student-T-Test, Chi-Square-Test und den Mann-Whitney U-Test analysiert. Das Signifikanzniveau lag bei 0,05. Zur Ermittlung extrinsischer Risikofaktoren diente ein logistisches Regressionsmodell. Ergebnisse: Bei 61 Katzen wurde eine Hyperthyreose diagnostiziert, was eine Prävalenz von 12,3% ergibt (95%-KI: 9,7–15,5). Ältere (p < 0,001) weibliche Katzen (p = 0,019; Odds Ratio 1,9) waren signifikant häufiger betroffen. Hauskatzen (Europäisch Kurz- und Langhaarkatzen) erkrankten häufiger als Rassekatzen (p = 0,016). Bei 164 Katzen wurde die Verdachtsdiagnose Hyperthyreose gestellt und in 20,1% (33/164) der Fälle verifiziert. In 2,4% (12/495) der Fälle war die erhöhte T4-Konzentration ein Zufallsbefund. Hyperthyreote Katzen wurden häufiger mit Nassfutter aus Aluminiumschalen (p < 0,013) gefüttert als nichthyperthyreote Katzen. Schlussfolgerung und klinische Re levanz: Ältere, weibliche Hauskatzen sind prädisponiert, an einer Schilddrüsenüberfunktion zu erkranken. Die Diagnose lässt sich häufig nach initialem klinischem Verdacht stellen, woraus in der Studienpopulation eine Prävalenz von 12,3% resultierte. Rückstände aus Aluminiumschalen oder das Nassfutter selbst scheinen eine Rolle in der Ätiopathogenese zu spielen.

Effects of dietary selenium and moisture on the physical activity and thyroid axis of cats

Consumption of canned cat food is considered a risk factor for the development of feline hyperthyroidism. Because selenium and water are substantially higher in canned diets compared to dry diets, objectives of this study were to determine whether increased dietary selenium or water alters the function of the hypothalamic-pituitary-thyroid axis and leads to an increase in activity level. Employing a 28-day latin square design with a 14-day washout, six lean, neutered male domestic shorthair cats were fed (i) commercially available adult dry feline diet containing 0.8 ppm selenium (control), (ii) control diet with added sodium selenite to achieve a dietary selenium concentration of 1.125 ppm (selenium treatment) and (iii) the control diet with additional water to achieve a moisture content of 75% wt/wt (water treatment). Water consumption was determined using deuterium oxide washout. Actical activity monitors were placed on each cat's collar to allow quantification of the activity of each cat. Circulating serum T3 and T4 was measured on days 0, 14, and 28. On day 28, a thyrotropin-releasing hormone (TRH) stimulation test was conducted to determine treatment effects on serum concentrations of thyroid hormones. There was a significant increase in daily water consumption with dietary water treatment (192 ml ± 7.85 SEM) compared to the control (120 ml ± 20.4) and selenium (116 ml ± 14.6) treatments. Both water and selenium treatments were associated with greater (p < .05) activity over that of the control treatment by 20.5% and 11% respectively. Serum TT3 AUC concentrations (0-4 hr) of TRH stimulation tests were greater (p < .05) by 16% with water compared to control treatments. The results of this study indicate that dietary water content may alter the function of the thyroid axis and that this effect is associated with an increase in physical activity.

Prevalence of and risk factors for feline hyperthyroidism in South Africa

Objectives Hyperthyroidism is a disorder of older cats that may have a geographical variation in prevalence. Prevalence studies have not yet been performed in South Africa, a geographical area where hyperthyroidism in cats has recently been observed and where, reportedly, the incidence appears to be increasing. The purpose of this study was to determine the prevalence of feline hyperthyroidism in South Africa and to identify any potential risk factors. Further information on the worldwide prevalence and possible causative factors would increase our understanding of the aetiology of this disease and help identify any preventive measures. Methods Serum total thyroxine (tT4) and canine thyroid-stimulating hormone (cTSH) were measured in 302 cats aged 9 years and older that were presented at various veterinary clinics throughout South Africa. In cats with equivocal tT4 and undetectable cTSH values, serum free thyroxine (fT4) was also measured. At the time of blood sampling a questionnaire was completed regarding vaccination history, internal and external parasite control, diet and environment. Results Prevalence of hyperthyroidism (tT4 >50 nmol/l or tT4 between 30 and 50 nmol/l with TSH <0.03 ng/ml and fT4 >50 pmol/l) was 7% (95% confidence interval 4.4-10.4), with no significant difference between healthy (5%) and sick (8%) cats. Cats ⩾12 years of age (odds ratio [OR] 4.3, P = 0.02) and cats eating canned food (OR 2.1, P = 0.1) were more likely to be diagnosed with hyperthyroidism. No significant relationship between vaccinations, parasite control or indoor environment and hyperthyroidism was observed. Hyperthyroid cats were more likely to present with weight loss (OR 3.2, P = 0.01) and with a heart rate ⩾200 beats per min (OR 5, P = 0.01) than cats without the disease. Conclusions and relevance Hyperthyroidism does not appear to be uncommon in the South African cat population. Risk factors for hyperthyroidism, specifically older age and eating canned food, were present in this as in other reported populations.

Breed, Coat Color, and Hair Length as Risk Factors for Hyperthyroidism in Cats

Background

Hyperthyroidism is very common in older cats, but the etiopathogenesis is poorly understood. Decreased risk of hyperthyroidism has been reported in certain colorpoint breeds, and this observation previously has been hypothesized to result from relatively greater tyrosine availability for thyroid hormone production because of limited ability to convert tyrosine to melanin pigment. However, studies investigating a potential link between coat pigmentation and risk of hyperthyroidism are limited.

Objective

To identify associations between coat phenotype and hyperthyroidism by investigation of breed, coat color, and hair length as risk factors for the disease.

Animals

Data were used from 4,705 cats aged ≥10 years, referred to a single veterinary teaching hospital (2006–2014) in the United Kingdom.

Methods

Retrospective, epidemiological, cross‐sectional study using Bayesian multivariable logistic regression to assess risk factors for hyperthyroidism.

Results

Burmese (odds ratio [OR], 0.01; 0.00–0.23; P = .004), Tonkinese (OR, 0.05; 0.00–0.95; P = .046), Persian (OR, 0.21; 0.10–0.44; P < .001), Siamese (OR, 0.27; 0.12–0.61; P = .002), Abyssinian (OR, 0.04; 0.00–0.74; P = .031), and British shorthair (OR, 0.47; 0.28–0.79; P = .004) breeds had decreased risk of hyperthyroidism compared to domestic shorthairs. Longhaired, nonpurebred cats (OR, 1.30; 1.03–1.64; P = .028) were at increased risk of hyperthyroidism. Coat color/pattern was not associated with hyperthyroidism in nonpurebred cats.

Conclusions and Clinical Importance

We identified decreased risk of hyperthyroidism in the Tonkinese, Abyssinian, and British shorthair breeds, identified an association between risk of hyperthyroidism and hair length, and confirmed decreased risk in Burmese, Siamese, and Persian breeds. Additional studies are warranted to further investigate these findings.

The Effect of Moderate Dietary Protein and Phosphate Restriction on Calcium-Phosphate Homeostasis in Healthy Older Cats

Background

Dietary phosphate and protein restriction decreases plasma PTH and FGF‐23 concentrations and improves survival time in azotemic cats, but has not been examined in cats that are not azotemic.

Hypothesis

Feeding a moderately protein‐ and phosphate‐restricted diet decreases PTH and FGF‐23 in healthy older cats and thereby slows progression to azotemic CKD.

Animals

A total of 54 healthy, client‐owned cats (≥ 9 years).

Methods

Prospective double‐blinded randomized placebo‐controlled trial. Cats were assigned to test diet (protein 76 g/Mcal and phosphate 1.6 g/Mcal) or control diet (protein 86 g/Mcal and phosphate 2.6 g/Mcal) and monitored for 18 months. Changes in variables over time and effect of diet were assessed by linear mixed models.

Results

A total of 26 cats ate test diet and 28 cats ate control diet. There was a significant effect of diet on urinary fractional excretion of phosphate (P = 0.045), plasma PTH (P = 0.005), and ionized calcium concentrations (P = 0.018), but not plasma phosphate, FGF‐23, or creatinine concentrations. Plasma PTH concentrations did not significantly change in cats fed the test diet (P = 0.62) but increased over time in cats fed the control diet (P = 0.001). There was no significant treatment effect of the test diet on development of azotemic CKD (3 of 26 (12%) test versus 3 of 28 (11%) control, odds ratio 1.09 (95% CI 0.13–8.94), P = 0.92).

Conclusions and Clinical Importance

Feeding a moderately protein‐ and phosphate‐restricted diet has effects on calcium‐phosphate homeostasis in healthy older cats and is well tolerated. This might have an impact on renal function and could be useful in early chronic kidney disease.

2016 AAFP Guidelines for the Management of Feline Hyperthyroidism

CLINICAL CONTEXT

Since 1979 and 1980 when the first reports of clinical feline hyperthyroidism (FHT) appeared in the literature, our understanding of the disease has evolved tremendously. Initially, FHT was a disease that only referral clinicians treated. Now it is a disease that primary clinicians routinely manage. Inclusion of the measurement of total thyroxine concentration in senior wellness panels, as well as in diagnostic work-ups for sick cats, now enables diagnosis of the condition long before the cat becomes the classic scrawny, unkempt, agitated patient with a bulge in its neck. However, earlier recognition of the problem has given rise to several related questions: how to recognize the health significance of the early presentations of the disease; how early to treat the disease; whether to treat FHT when comorbid conditions are present; and how to manage comorbid conditions such as chronic kidney disease and cardiac disease with treatment of FHT. The 2016 AAFP Guidelines for the Management of Feline Hyperthyroidism (hereafter referred to as the Guidelines) will shed light on these questions for the general practitioner and suggest when referral may benefit the cat.

SCOPE

The Guidelines explain FHT as a primary disease process with compounding factors, and provide a concise explanation of what we know to be true about the etiology and pathogenesis of the disease.The Guidelines also:Distill the current research literature into simple recommendations for testing sequences that will avoid misdiagnosis and separate an FHT diagnosis into six clinical categories with associated management strategies.Emphasize the importance of treating all hyperthyroid cats, regardless of comorbidities, and outline the currently available treatments for the disease.Explain how to monitor the treated cat to help avoid exacerbating comorbid diseases.Dispel some of the myths surrounding certain aspects of FHT and replace them with an evidence-based narrative that veterinarians and their practice teams can apply to feline patients and communicate to their owners.

EVIDENCE BASE

To help ensure better case outcomes, the Guidelines reflect currently available, evidenced-based knowledge. If research is lacking, or if a consensus does not exist, the expert panel of authors has made recommendations based on their extensive, cumulative clinical experience.

Risk Factors for Development of Chronic Kidney Disease in Cats

BACKGROUND

Identification of risk factors for development of chronic kidney disease (CKD) in cats may aid in its earlier detection.

HYPOTHESIS/OBJECTIVES

Evaluation of clinical and questionnaire data will identify risk factors for development of azotemic CKD in cats.

ANIMALS

One hundred and forty-eight client-owned geriatric (>9 years) cats.

METHODS

Cats were recruited into the study and followed longitudinally for a variable time. Owners were asked to complete a questionnaire regarding their pet at enrollment. Additional data regarding dental disease were obtained when available by development of a dental categorization system. Variables were explored in univariable and multivariable Cox regression models.

RESULTS

In the final multivariable Cox regression model, annual/frequent vaccination (P value, .003; hazard ratio, 5.68; 95% confidence interval, 1.83-17.64), moderate dental disease (P value, .008; hazard ratio, 13.83; 95% confidence interval, 2.01-94.99), and severe dental disease (P value, .001; hazard ratio, 35.35; 95% confidence interval, 4.31-289.73) predicted development of azotemic CKD.

CONCLUSION

Our study suggests independent associations between both vaccination frequency and severity of dental disease and development of CKD. Further studies to explore the pathophysiological mechanism of renal injury for these risk factors are warranted.

Temporal Changes of PBDE Levels in California House Cats and a Link to Cat Hyperthyroidism

In this study, we measured serum PBDE levels in California (CA) house cats during two time periods: 2008-2010 and 2012-2013 to assess the impacts of the decline in use of these materials after the bans. The median ∑19PBDE level in CA household cats (age ≥10 yr) was 3479 ng/g lipid in 2008-2010 (1st time period, n = 21) and 1518 ng/g lipid in 2012-2013 (2nd time period, n = 22), about 2 times lower than in the first time period (p = 0.006). In contrast, PCB and OCP levels showed no statistically significant changes. With better matched group size and age (HT = 11 vs non-HT = 11, age ≥10 yr) in the second time period, we found that ∑19PBDE level (mean ± SE ng/g lipid) was significantly higher in the HT group (3906 ± 1442) than those in the non-HT group (1125 ± 244) (p = 0.0030). Higher levels of PCBs and OCPs were also found in HT group. Despite the declines of PBDE levels, our findings indicate that the current levels of PBDEs, as well as PCBs and OCPs, may still pose health effects for house cats and, possibly, humans.

A critical review of food-associated factors proposed in the etiology of feline hyperthyroidism

Since the first description of feline hyperthyroidism (HT) in 1979, several studies have been undertaken to define the etiology of the disease. Epidemiologic studies, after investigating non-food- and food-associated factors, suggest a multifactorial etiology. However, in the absence of prospective cohort studies that can confirm a cause-and-effect relationship between HT and associated risk factors, no causative factor for HT has been identified to date. Feline HT resembles toxic nodular goiter in humans, with autonomously functioning upregulated iodide uptake systems. Contribution of the diet to HT development remains controversial. The purpose of this paper is to review critically the reported food-associated risk factors for HT.

Higher PBDE serum concentrations may be associated with feline hyperthyroidism in Swedish cats

Serum from 82 individual cats was analyzed for decabromobiphenyl (BB-209), polybrominated diphenyl ethers (PBDEs), hydroxylated PBDEs (OH-PBDEs), and 2,4,6-TBP in order to study differences in body burden between healthy and sick cats diagnosed with Feline Hyperthyroidism (FH). Within the study group, 60 of these cats had a euthyroid (n = 23) or hyperthyroid (n = 37) status, all of which were used in the comparison. This study shows that hyperthyroid compared to euthyroid cats have higher serum concentrations for some of the investigated PBDEs (BDE-99, BDE-153, and BDE-183) and CB-153 on a fat weight basis. Further, it is intriguing, and beyond explanation, why the flame retardant BB-209 (discontinued in 2000) is present in all of the cat serum samples in concentrations similar to BDE-209. Median BDE-47/-99 ratios are 0.47 and 0.32 for healthy and euthyroid cats, respectively, which differs significantly from Swedes, where the ratio is 3.5. Another important finding is the occurrence of very low levels or the absence of hydroxylated PBDE metabolites in the cats. In addition, the major OH-PBDE, 6-OH-BDE47, is likely of natural origin, probably ingested via cat food. The statistics indicate an association between elevated PBDE concentrations in the cats and FH.

Evaluation of polybrominated diphenyl ethers (PBDEs) in matched cat sera and house dust samples: investigation of a potential link between PBDEs and spontaneous feline hyperthyroidism

The cause of feline hyperthyroidism (FH), a common endocrinopathy of domestic cats, is unknown. A potential association between exposure to environmental contaminants polybrominated diphenyl ethers (PBDEs) and FH was investigated. The median serum level for the sum of congeners BDE-47, BDE-99, BDE-153, BDE-154 and BDE-183 (Σ5) in hyperthyroid and euthyroid cats was 82 and 174 ng g(-1)lw respectively with no significant difference in PBDE levels or profiles between groups. Overall, the median (min to max) concentration of PBDEs in cat serum (n=65) was 118 ng g(-1)lw (5-5260 ng g(-1)lw), which is approximately 10 times higher than that observed in the Australian human population. Furthermore, congener composition in feline serum samples was dominated by congener BDE-99, followed by BDE-47 then BDE-153 which differs from results of human biomonitoring. There was no correlation between PBDE levels in feline serum samples and matched house dust samples (n=25). However the similarity of BDE-47/99 ratio in each matrix suggests dust is likely the dominant exposure. Calculation of the daily exposure dose via dust ingestion for cats equated to a mean of 33 ng kg(-1) bw d(-1) (0.2-150 ng kg(-1) bw d(-1)). Differences in exposure estimates for Australian and US cats, based on dust ingestion alone, are consistent with the observed differences in body burdens. Our results do not support a role for PBDE exposure in the aetiopathogenesis of FH.

Perioperative anaesthetic care of the cat undergoing dental and oral procedures: key considerations

CLINICAL CHALLENGES

Anaesthesia for dental and oral procedures in cats can be challenging and many factors need to be taken into consideration. Often it is older patients requiring these procedures and, while old age itself is not a contraindication for general anaesthesia, older patients tend to have limited homeostatic reserves and are, therefore, more prone to anaesthesia-induced insults of vital organs. Most sedative and anaesthetic agents have cardiovascular side effects, which may result in detrimental consequences in older patients in which organ reserves are likely reduced.

AIMS

The need for good patient assessment and management during the entire perianaesthetic period cannot be overemphasised. This article describes how both anaesthetic protocol and intravenous fluid therapy should be tailored to the individual cat's needs. Application of a multimodal analgesic protocol (the combination of different analgesic agents) and a balanced anaesthetic technique incorporating local nerve blocks is highly recommended and a particular focus of the review. The use of local anaesthetic agents for the latter not only provides optimal pre-emptive analgesia, but also reduces the amount of anaesthetic agents needed to maintain an adequate level of anaesthesia and, therefore, limits their side effects. Other key aspects of perianaesthetic care of the feline dental and oral patient include airway protection, monitoring and maintenance of body temperature, eye protection, and analgesia extending well into the post-anaesthetic period.

EVIDENCE BASE

The authors draw on their clinical experience and the referenced literature to provide a practical overview of this critical but often-overlooked aspect of feline dentistry.

Animal models of disease: feline hyperthyroidism: an animal model for toxic nodular goiter

Since first discovered just 35 years ago, the incidence of spontaneous feline hyperthyroidism has increased dramatically to the extent that it is now one of the most common disorders seen in middle-aged to senior domestic cats. Hyperthyroid cat goiters contain single or multiple autonomously (i.e. TSH-independent) functioning and growing thyroid nodules. Thus, hyperthyroidism in cats is clinically and histologically similar to toxic nodular goiter in humans. The disease in cats is mechanistically different from Graves' disease, because neither the hyperfunction nor growth of these nodules depends on extrathyroidal circulating stimulators. The basic lesion appears to be an excessive intrinsic growth capacity of some thyroid cells, but iodine deficiency, other nutritional goitrogens, or environmental disruptors may play a role in the disease pathogenesis. Clinical features of feline toxic nodular goiter include one or more palpable thyroid nodules, together with signs of hyperthyroidism (e.g. weight loss despite an increased appetite). Diagnosis of feline hyperthyroidism is confirmed by finding the increased serum concentrations of thyroxine and triiodothyronine, undetectable serum TSH concentrations, or increased thyroid uptake of radioiodine. Thyroid scintigraphy demonstrates a heterogeneous pattern of increased radionuclide uptake, most commonly into both thyroid lobes. Treatment options for toxic nodular goiter in cats are similar to that used in humans and include surgical thyroidectomy, radioiodine, and antithyroid drugs. Most authorities agree that ablative therapy with radioiodine is the treatment of choice for most cats with toxic nodular goiter, because the animals are older, and the disease will never go into remission.

Feline hyperthyroidism reported in primary-care veterinary practices in England: prevalence, associated factors and spatial distribution

Feline hyperthyroidism is a commonly diagnosed endocrinopathy that can have a substantial deleterious impact on the welfare of affected cats. This study aimed to estimate the prevalence, associated factors and geographical distribution for feline hyperthyroidism in England, using primary-care veterinary practice clinical data from the VetCompass Animal Surveillance Project. Prevalence was estimated from the overall cat cohort. Associated factor analysis used an age-matched, nested, case-control design with multivariable logistic regression. There were 2,276 cases of feline hyperthyroidism identified from 95,629 cats attending 84 practices from September 2009 to December 2011. Cases were aged 6-25 years. 3.7 per cent of cases and 9.9 per cent of controls were purebred, 56.4 per cent of cases and 56.5 per cent of controls were female, and 88.1 per cent of cases and 86.0 per cent of controls were neutered. The apparent prevalence was 2.4 per cent (95% CI 2.3 to 2.5 per cent) overall, and 8.7 per cent (95% CI 8.3 to 9.0 per cent) in cats aged 10 years or above. Burmese (OR 0.15, 95% CI 0.07 to 0.32, P<0.0001), Persian (OR 0.17, 95% CI 0.08 to 0.33, P<0.0001), Siamese (OR 0.4, 95% CI 0.21 to 0.75, P=0.004) and purebred cats overall (OR 0.33, 95% CI 0.25 to 0.42, P< 0.0001) had lower odds of feline hyperthyroidism than non-purebred cats. Insured cats had increased odds (OR 1.78, 95% CI 1.56 to 2.03, P< 0.001). There was little evidence of spatial variation. This study highlights feline hyperthyroidism as a high-prevalence disease in England, and reports reduced odds of diagnosis in certain breeds and purebred cats overall.

Worldwide prevalence and risk factors for feline hyperthyroidism: A review

Since first reported in the late 1970s, there has been a steady but dramatic increase in the worldwide prevalence of hyperthyroidism in cats. It is now regarded as the most common feline endocrine disorder, with diabetes mellitus coming a close second. Not only is there evidence for an increased worldwide prevalence of feline hyperthyroidism, but also for geographical variation in the prevalence of the disease. Despite its frequency, the underlying cause(s) of this common disease is or are not known, and therefore prevention of the disease is not possible. Due to the multiple risk factors that have been described for feline hyperthyroidism, however, it is likely that more than one factor is involved in its pathogenesis. Continuous, lifelong exposure to environmental thyroid-disruptor chemicals or goitrogens in food or water, acting together or in an additive fashion, may lead to euthyroid goitre and ultimately to autonomous adenomatous hyperplasia, thyroid adenoma and hyperthyroidism. This review aims to summarise the available published evidence for the changes observed in the worldwide prevalence of the disease, as well as risk factors that may contribute to development of hyperthyroidism in susceptible cats.

Iodine concentration in commercial cat foods from three regions of the USA, 2008-2009

Fluctuations in iodine concentration in food have been suggested as one risk factor for the development of feline hyperthyroidism, an epidemic disease first described in 1979. Three international studies have examined iodine concentrations of commercial cat foods. The iodine concentration of 112 commercial cat foods from across the USA was measured, and the daily iodine intake by hypothetical 4.5 kg adult cats or 1.4 kg kittens calculated in this descriptive epidemiologic study to examine differences in feline iodine intake due to (i) geographical source of foods, (ii) packaging type, (iii) brand-to-brand variation, (iv) form of iodine supplementation, (v) types and numbers of seafood ingredients and (vi) kitten and 'therapeutic' diets. Dramatic variation among canned foods (resulting in ingestion of approximately 49-9639 μg iodine/day) suggests that the disparity in iodine concentrations may lead to development of nodular hyperplasia and, later, clinical hyperthyroidism, if cats consume diets that are at first iodine-deficient and later contain excessive iodine. Manufacturers are encouraged to ensure adequate iodine supplementation across all products and areas of the USA.

Hyperthyroidism in cats: what's causing this epidemic of thyroid disease and can we prevent it?

PRACTICAL RELEVANCE

Since first being reported in the late 1970s, there has been a dramatic increase in the prevalence of hyperthyroidism in cats. It is now recognized worldwide as the most common feline endocrine disorder.

PATIENT GROUP

Hyperthyroidism is an important cause of morbidity in cats older than 10 years of age. It is estimated that over 10% of all senior cats will develop the disorder.

CLINICAL CHALLENGES

Despite its frequency, the underlying cause(s) of this common disease is/are not known, and no one has suggested a means to prevent the disorder. Because of the multiple risk factors that have been described for feline hyperthyroidism, it is likely that more than one factor is involved in its pathogenesis. Continuous, lifelong exposure to environmental thyroid disruptor chemicals or goitrogens in food or water, acting together in an additive or synergistic manner, may first lead to euthyroid goiter and then to autonomous adenomatous hyperplasia, thyroid adenoma and hyperthyroidism.

EVIDENCE BASE

This review draws on published research studies to summarize the available evidence about the risk factors for feline hyperthyroidism. Based on the known goitrogens that may be present in the cat's food, drinking water or environment, it proposes measures that cat owners can implement that might prevent, or reduce the prevalence of, thyroid tumors and hyperthyroidism in their cats.

High polybrominated diphenyl ether levels in California house cats: house dust a primary source?

Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants that act as endocrine disruptors, affecting thyroid hormone homeostasis. As a follow-up to a recent study showing high PBDE levels in household cats and linking PBDE levels with cat hyperthyroidism, we measured PBDEs, polychlorinated biphenyls (PCBs), and organochlorinated pesticides (OCPs) in serum samples from 26 California household cats (16 hyperthyroid, 10 controls) using liquid-liquid extraction and high-resolution gas chromatography/high-resolution mass spectrometry. In the present pilot study, we found that PBDE levels in California house cats were extremely high (ΣPBDEs median = 2,904 ng/g lipid; range, 631-22,537 ng/g lipid). This is approximately 50 times higher than levels in California residents (ΣPBDEs geomean = 62 ± 8.9 ng/g lipid, National Health and Nutrition Examination Survey), who have among the highest human levels in the world. Polybrominated diphenyl ethers congener patterns (BDE-99 major congener, BDE-209 significant) differed markedly from patterns found in California residents (BDE-47 major) or wildlife but resembled patterns found in house dust. Polychlorinated biphenyls and OCPs in cats were highly correlated, consistent with a shared dietary source or pathway of exposure, but did not correlate with PBDEs. This suggests a different source or pathway of exposure for PBDEs, which was most likely house dust. The authors found no evidence that linked levels of PBDEs, PCBs, or OCPs with hyperthyroidism. This may be because of the small sample size, competing or confounding risk factors, or complicated causal mechanisms.

Feline hyperthyroidism: potential relationship with iodine supplement requirements of commercial cat foods

ARTICLE RATIONALE: Since the late 1970s, there has been a significant increase in the prevalence of feline hyperthyroidism (FH). It is now recognized worldwide as the most common endocrinopathy of older cats, resembling toxic nodular goiter of older humans in iodine-deficient areas. The purpose of this article is to identify the potential for iodine concentrations in the diet to contribute to the etiology of FH. HISTORICAL CONTEXT: Iodine concentrations of commercial cat foods vary widely. A review of historical iodine recommendations revealed that the units of iodine supplementation changed in the 1970s. Given this change, foods minimally supplemented since the late 1970s would have been iodine deficient for most cats.

PRACTICAL RELEVANCE

Iodine supplementation of commercial cat foods should be evaluated in the light of the iodine recommendations revised in 2006. Foods may remain deficient in iodine if supplemented at the minimum recommended concentration, possibly contributing to the development of FH.