Iatrogenic Primary Hypothyroidism Associated With Sulfamethoxazole-Trimethoprim Treatment of Nocardiosis in a Cat.

A 9-year-old mixed breed cat with a history of recurrent ulcerated skin lesions was diagnosed with nocardiosis. Three months after initiating potentiated sulfonamide treatment, the cat developed goitrous hypothyroidism, characterized by palpable enlargement of both thyroid lobes, low serum concentrations of total thyroxine (T4) and free thyroxine (fT4), and high serum thyroid-stimulating hormone (TSH) concentration. Thyroid scintigraphy identified symmetrical enlargement of both thyroid lobes, with increased radionuclide (Tc-pertechnetate) uptake.

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.

Blood pressure in hyperthyroid cats before and after radioiodine treatment.

Background: Hyperthyroid cats commonly have systemic hypertension, with a reported prevalence of 7% to 48%. Although hypertension might be expected to resolve once treatment restores euthyroidism, it can persist or only first develop after treatment.

Objectives: To determine the proportion of hyperthyroid cats with hypertension (systolic blood pressure [SBP] ≥160 mm Hg), persistence or first development of hypertension after successful radioiodine treatment, and correlation of post-treatment hypertension with azotemia or hypothyroidism.

Evaluation of a novel, sensitive thyroid-stimulating hormone assay as a diagnostic test for thyroid disease in cats.

Objective: Clinicians commonly use thyroid-stimulating hormone (TSH) concentrations to diagnose thyroid disorders in humans and dogs. In cats, canine TSH chemiluminescent immunoassays (CLIA) assays are commonly used to measure TSH, but these TSH-CLIAs cannot measure low TSH concentrations (< 0.03 ng/mL) and therefore cannot distinguish between low-normal concentrations and truly low TSH concentrations (characteristic of hyperthyroidism).

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.

Biological variation of serum thyrotropin and thyroid hormones concentrations determined at 8-week intervals for 1 year in clinically healthy cats.

Background: Cats commonly develop thyroid disease but little is known about the long-term biological variability of serum thyroid hormone and thyrotropin (thyroid-stimulating hormone; TSH) concentrations.

Objectives: We aimed to determine the long-term biological variation of thyroid hormones and TSH in clinically healthy cats.

Methods: A prospective, observational study was carried out.

Biological variation of biochemical analytes determined at 8-week intervals for 1 year in clinically healthy cats.

Background: Biological variation helps determine whether population-based or subject-based reference intervals are more appropriate to assess changes in serial analytical values. Previous studies have investigated the biological variation of biochemical analytes weekly or with variable frequency over 5-14 weeks in cats, but none have considered biological variation at less frequent intervals over 1 year.

Objectives: We aimed to evaluate the long-term biological variation of 19 biochemical analytes in clinically healthy cats.

Effect of radioiodine treatment on muscle mass in hyperthyroid cats.

Background: Approximately 75% of hyperthyroid cats lose muscle mass as accessed with a muscle condition scoring (MCS) system. After treatment, MCS improves as the cats regain muscle mass.

Objectives: To quantify the degree of muscle loss in hyperthyroid cats using ultrasonography and evaluate changes in muscle mass after treatment.

Association of recessive c.430G>A (p.(Gly144Arg)) thyroid peroxidase variant with primary congenital hypothyroidism in cats.

Background: Primary congenital hypothyroidism (CH) is a rare endocrine disorder in cats with a largely unknown genetic cause.

Objectives: Describe the clinical presentation of CH in 11 affected cats and identify the causal genetic variant.

Animals: Eleven CH-cats from 10 unrelated families, 11 CH-free family members, 21 unrelated CH-free cats, and 155 unrelated nondiagnosed cats from different breeds.

Radioiodine treatment of hyperthyroidism in cats: results of 165 cats treated by an individualised dosing algorithm in Spain.

Objectives: Although radioiodine (I) is the treatment of choice for feline hyperthyroidism, I-dosing protocols commonly induce iatrogenic hypothyroidism and expose azotaemia. A recently reported patient-specific I dosing algorithm minimised the risk of I-induced hypothyroidism and azotaemia, while maintaining high cure rates. The aim of the study was to report results of I treatment in a European population of hyperthyroid cats using this patient-specific dosing algorithm.

Predicting outcomes in hyperthyroid cats treated with radioiodine.

Background: Radioiodine ( I) is the treatment of choice for cats with hyperthyroidism. After I, however, euthyroidism is not always achieved, with 5% to 10% of cats remaining persistently hyperthyroid and 20% to 50% developing iatrogenic hypothyroidism.

Objectives: To identify pretreatment factors that may help predict persistent hyperthyroidism and iatrogenic hypothyroidism after treatment of cats using a novel I dosing algorithm.

A dosing algorithm for individualized radioiodine treatment of cats with hyperthyroidism.

Background: Radioiodine ( I) is the treatment of choice for hyperthyroidism in cats, but current I-dosing protocols can induce iatrogenic hypothyroidism and expose azotemia.

Objectives: To develop a cat-specific algorithm to calculate the lowest I dose to resolve hyperthyroidism, while minimizing risk of iatrogenic hypothyroidism and subsequent azotemia.

Animals: One thousand and four hundred hyperthyroid cats treated with I.

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

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

Biologic variation of symmetric dimethylarginine and creatinine in clinically healthy cats.

Background: Biologic variation of biochemical analytes, both within individuals and between individuals, determines whether population-based reference intervals (RIs) are appropriate when interpreting if a particular change is clinically relevant for a specific individual.

Objectives: We aimed to evaluate the biologic variation of symmetric dimethylarginine (SDMA) in clinically healthy cats.

Methods: A prospective, observational study was performed in which 10 clinically healthy, client-owned cats were sampled for serum biochemical analyses once weekly for 6 weeks.

Hyperthyroidism in Cats: Considering the Impact of Treatment Modality on Quality of Life for Cats and Their Owners.

In cats, hyperthyroidism can be treated in 4 ways: medical management with methimazole or carbimazole, nutritional management (low-iodine diet), surgical thyroidectomy, and radioactive iodine (I). Each form of treatment has advantages and disadvantages that should be considered when formulating a treatment plan for the individual hyperthyroid cat. Medical and nutritional managements are considered "reversible" or palliative treatments, whereas surgical thyroidectomy and I are "permanent" or curative treatments.

Hyperthyroidism is not a risk factor for subclinical bacteriuria in cats: A prospective cohort study.

Background: Subclinical bacteriuria is defined as a positive bacterial urine culture in the absence of clinical evidence of urinary tract infection (UTI). Studies have reported that hyperthyroid cats have UTIs (mostly subclinical) with prevalence rates of 12%-22%. Consequently, clinicians consider hyperthyroidism a risk factor for development of subclinical bacteriuria, and many recommend urine culture when evaluating hyperthyroid cats.

Short-term biological variation of serum thyroid hormones concentrations in clinically healthy cats.

Thyroid disease is common in cats, but little is known about the biologic variability of serum thyroid hormone concentrations and its impact on diagnostic utility in either healthy cats or cats with thyroid disease. The purpose of this study was to determine the biological variation, index of individuality, and reference change values for thyroid hormones and thyroid-stimulating hormone (TSH) in clinically healthy cats. Serum samples for analysis of total thyroxine (T), triiodothyronine (T), free T by dialysis, and TSH were obtained weekly for 6 wk from 10 healthy cats, then frozen until single-batch analyzed.

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.

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.

Contrast-enhanced ultrasound complements two-dimensional ultrasonography in diagnosing gallbladder diseases in dogs.

Gall-bladder diseases are common in dogs and two-dimensional ultrasonography is a current standard method for diagnosis and treatment planning. However, findings from this modality can be nonspecific. The aim of this retrospective, case series study was to describe conventional and contrast-enhanced ultrasound (using SonoVue ) findings in a group of dogs with histologically confirmed gall bladder disease.

Evaluation of Serum Symmetric Dimethylarginine Concentration as a Marker for Masked Chronic Kidney Disease in Cats With Hyperthyroidism.

Background: Hyperthyroidism can complicate (mask) the diagnosis of chronic kidney disease (CKD) because it increases glomerular filtration rate and decreases body muscle mass, both of which can lower serum creatinine concentrations. Currently, there is no clinical test that can reliably predict which hyperthyroid cats have concurrent azotemic CKD that will become apparent after treatment of the hyperthyroidism.

Objectives: To investigate serum symmetric dimethylarginine (SDMA) concentration as a potential marker of masked azotemia in untreated hyperthyroid cats.

Serum thyroxine and thyroid-stimulating hormone concentration in hyperthyroid cats that develop azotaemia after radioiodine therapy.

Objectives: The objectives of this study were to determine which serum thyroid hormone test best identifies iatrogenic hypothyroidism in cats that develop azotaemia after radioiodine treatment and to determine which thyroid test best differentiates these azotaemic, hypothyroid cats from azotaemic, radioiodine-treated euthyroid cats, as well as from azotaemic cats with chronic kidney disease and no history of thyroid disease.

Materials And Methods: A total of 42 hyperthyroid cats that developed azotaemia (serum creatinine ê220 µmol/L) after radioiodine treatment had serum concentrations of thyroxine and free thyroxine by dialysis and thyroid--stimulating hormone measured at 3, 6 and 12 months. Iatrogenic hypothyroidism was confirmed (n=28) or excluded (n=14) on the basis of thyroid scintigraphy.

Comparison of in-clinic point-of-care and reference laboratory total thyroxine immunoassays for diagnosis and post-treatment monitoring of hyperthyroid cats.

Objectives The Catalyst One Chemistry Analyzer (IDEXX Laboratories) is a point-of-care instrument that can measure total thyroxine (TT4) by immunoassay. The aims of this study were to evaluate the analytic performance of the Catalyst TT4 assay in feline sera and to examine agreement of the Catalyst TT4 results with those measured by immunoassay at a veterinary reference laboratory. Methods Assay precision, reproducibility and linearity were evaluated for the Catalyst TT4 assay.

Thyroid Cysts in Cats: A Retrospective Study of 40 Cases.

Background: Thyroid cysts are rare in cats and poorly documented.

Objectives: To report distinguishing clinical features and treatment responses of cats with thyroid cysts.

Animals: Forty client-owned cats.

Efficacy of Low-dose (2 millicurie) versus Standard-dose (4 millicurie) Radioiodine Treatment for Cats with Mild-to-Moderate Hyperthyroidism.

Background: Radioiodine ( I) is effective treatment for hyperthyroidism in cats, but optimal dose to restore euthyroidism without inducing hypothyroidism is unclear. Treatment-induced hypothyroidism can lead to azotemia and reduced duration of survival.

Objective: To compare efficacy and short-term outcomes of low-dose I versus higher, standard-dose I as treatment for hyperthyroidism.