Recombinant human thyrotropin stimulation test in 114 dogs with suspected hypothyroidism: a cross-sectional study

Serum cholesterol disturbances in dogs with common endocrinopathies at the time of diagnosis: a retrospective study

BACKGROUND

Although dyslipidemia is commonly reported in dogs, comparative data on the magnitude of serum cholesterol disturbances have not been reported. We aimed to describe the severity of hyper- and hypocholesterolemia in dogs with common endocrinopathies and to evaluate its association with common laboratory parameters. Medical records were reviewed over a decade (2011-2022) for dogs with hypothyroidism, diabetes mellitus (DM), hyperadrenocorticism (HAC), or hypoadrenocorticism (HA), and included signalment, common laboratory and diagnostic imaging parameters, comorbidities, and medications. This retrospective study included 53 dogs with hypothyroidism, 54 with DM, 62 with HAC, and 79 with HA.

RESULTS

Medians [range] of serum cholesterol concentration ([Chol]s) for dogs with hypothyroidism, DM, HAC, and HA were 492 [174-1829], 321 [116-928], 309 [151-630], and 112 mg/dL [31-309], and hypercholesterolemia was reported in 91%, 85%, 81%, and 9% for each disorder, respectively. Median [Chol]s was significantly higher in hypothyroid dogs with a serum thyroxine concentration < 0.47 (A = 607) vs. ≥0.47 ug/dL (B = 324 mg/dL) (B-A = -299 mg/dL; 95.21% CI of difference = [-433; -166]; p < .0001), and significantly lower in HAC dogs with serum ALP activity < 1,000 U/L (A = 275) vs. ≥1,000 (B = 360 mg/dL) (B-A = + 74 mg/dL; 95.14% CI of difference = [+ 25; +121], p = .006). Comparison among all studied endocrinopathies showed that median [Chol]s was significantly higher in hypothyroid dogs and significantly lower in HA dogs, whereas median [Chol]s was similar in HAC and DM dogs.

CONCLUSIONS

Serum cholesterol concentration can serve as a valuable tool to suspect certain canine endocrinopathies.

L-thyroxine and 4-pregnane-3,20‑dione preserves pregnancy in bitches with hypothyroidism and hypoluteoidism

Hypoluteoidism is characterized by insufficient secretion of progesterone (P4) by the corpus luteum (CL) during pregnancy, resulting in embryonic resorption and miscarriage. In dogs, hypothyroidism can occur concurrently with hypoluteoidism, therefore, the aim of this study was to propose a combination therapy to treat these two conditions in bitches. The study included 30 bitches that were artificially inseminated and divided into three experimental groups. The control group (G1) included 10 bitches with a history of normal pregnancies, normal thyroid activity and P4 levels. This group received no clinical treatment. Treatment groups included 20 bitches diagnosed with reproductive hypothyroidism and hypoluteoidism: 10 dogs in the G2 group were treated with L-thyroxine (20 μg/kg/day) only and 10 dogs in the G3 group were treated with L-thyroxine and a long-acting synthetic P4 analogue (4-pregnane-3,20-dione, 1.0 mg/kg every 72 h until cesarean section on day 61). In all dogs, pregnancy and embryonic viability was monitored by ultrasound until term. G1 females had normal pregnancies (P4: day 24, 33.33 ± 2.95 ng/mL [106.00 ± 9.38 nmol/L]; day 38, 23.95 ± 1.21 ng/mL [76.16 ± 3.85 nmol/L]; day 50, 10.53 ± 0.82 ng/mL [33.49 ± 2.61 nmol/L]; day 63, 1.11 ± 0.22 ng/mL [3.53 ± 0.70 nmol/L]; p < 0.001). G2 females suffered embryonic death detected between day 31 and day 33 by ultrasound (P4: 4.67 ng/mL ± 0.41 ng/mL, [14.85 ± 1.30 nmol/L]; p < 0.001). In contrast, G3 females had similar plasma P4 levels to G1 dogs, and pregnancy was maintained until the scheduled cesarean section. These data suggest that combination therapy of L-thyroxine and 4-pregnane-3,20-dione maintains pregnancy to term in dogs with concomitant hypothyroidism and hypoluteoidism.

Effect of recombinant human thyroid stimulating hormone on radioactive iodine uptake by thyroid carcinoma in dogs

BACKGROUND

The high doses of radioiodine-131 (131I) and, subsequently, the high radioactive burden for dog and environment warrants optimization of 131I therapy in dogs with thyroid carcinoma (TC).

HYPOTHESIS/OBJECTIVES

To evaluate the effect of a revised protocol with recombinant human thyroid stimulating hormone (rhTSH) on tumor radioactive iodine uptake (RAIU) in dogs with TC.

ANIMALS

Nine client-owned dogs diagnosed with TC.

METHODS

A prospective cross-over study in which tumor RAIU was calculated and compared at 8 hours (8h-RAIU) and 24 hours (24h-RAIU) after injection of radioactive iodine-123 (123I), once with and once without rhTSH (ie, 250 μg, IM, 24 and 12 hours before 123I) in each dog. Simultaneously, serum total thyroxine (TT4) and TSH were measured at baseline (T0), and 6 (T6), 12 (T12), 24 (T24), and 48 hours (T48) after the first rhTSH administration.

RESULTS

Tumor RAIU was significantly higher at 24 hours with rhTSH compared to no rhTSH (mean difference = 8.85%, 95% CI of [1.56; 16.14]; P = .03), while this was non-significant at 8 hours (mean difference = 4.54%, 95% CI of [0.35; 8.73]; P = .05). A significant change of serum TT4 (median difference T24 - T0 = 35.86 nmol/L, interquartile range [IQR] = 15.74 nmol/L) and TSH (median difference T24 - T0 = 1.20 ng/mL, IQR = 1.55 ng/mL) concentrations occurred after administration of rhTSH (P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Recombinant human TSH could optimize 131I treatment in dogs with TC by increasing tumor RAIU and thus 131I treatment efficacy.

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

BACKGROUND

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

OBJECTIVES

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

ANIMALS

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

METHODS

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

RESULTS

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

CONCLUSIONS AND CLINICAL RELEVANCE

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

Development and internal validation of diagnostic prediction models using machine-learning algorithms in dogs with hypothyroidism

Introduction

Hypothyroidism can be easily misdiagnosed in dogs, and prediction models can support clinical decision-making, avoiding unnecessary testing and treatment. The aim of this study is to develop and internally validate diagnostic prediction models for hypothyroidism in dogs by applying machine-learning algorithms.

Methods

A single-institutional cross-sectional study was designed searching the electronic database of a Veterinary Teaching Hospital for dogs tested for hypothyroidism. Hypothyroidism was diagnosed based on suggestive clinical signs and thyroid function tests. Dogs were excluded if medical records were incomplete or a definitive diagnosis was lacking. Predictors identified after data processing were dermatological signs, alopecia, lethargy, hematocrit, serum concentrations of cholesterol, creatinine, total thyroxine (tT4), and thyrotropin (cTSH). Four models were created by combining clinical signs and clinicopathological variables expressed as quantitative (models 1 and 2) and qualitative variables (models 3 and 4). Models 2 and 4 included tT4 and cTSH, models 1 and 3 did not. Six different algorithms were applied to each model. Internal validation was performed using a 10-fold cross-validation. Apparent performance was evaluated by calculating the area under the receiver operating characteristic curve (AUROC).

Results

Eighty-two hypothyroid and 233 euthyroid client-owned dogs were included. The best performing algorithms were naive Bayes in model 1 (AUROC = 0.85; 95% confidence interval [CI] = 0.83-0.86) and in model 2 (AUROC = 0.98; 95% CI = 0.97-0.99), logistic regression in model 3 (AUROC = 0.88; 95% CI = 0.86-0.89), and random forest in model 4 (AUROC = 0.99; 95% CI = 0.98-0.99). Positive predictive value was 0.76, 0.84, 0.93, and 0.97 in model 1, 2, 3, and 4, respectively. Negative predictive value was 0.89, 0.89, 0.99, and 0.99 in model 1, 2, 3, and 4, respectively.

Discussion

Machine learning-based prediction models were accurate in predicting and quantifying the likelihood of hypothyroidism in dogs based on internal validation performed in a single-institution, but external validation is required to support the clinical applicability of these models.

2023 AAHA Selected Endocrinopathies of Dogs and Cats Guidelines

Canine and feline endocrinopathies reflect an endocrine gland disease or dysfunction with resulting hormonal abnormali ties that can variably affect the patient's wellbeing, quality of life, and life expectancy. These guidelines provide consensus recommendations for diagnosis and treatment of four canine and feline endocrinopathies commonly encountered in clini cal practice: canine hypothyroidism, canine hypercortisolism (Cushing's syndrome), canine hypoadrenocorticism (Addi son's disease), and feline hyperthyroidism. To aid the general practitioner in navigating these common diseases, a stepwise diagnosis and treatment algorithm and relevant background information is provided for managing each of these diseases. The guidelines also describe, in lesser detail, the diagnosis and treatment of three relatively less common endo crinopathies of cats: feline hyperaldosteronism, feline hypothyroidism, and feline hyperadrenocorticism. Additionally, the guidelines present tips on effective veterinary team utilization and client communication when discussing endocrine cases.