Hyperadrenocorticism associated with sex steroid excess

What Kinds of Dogs Are Used in Clinical and Experimental Research?

Simple Summary

The objective of this study was to evaluate the signalment of dogs used in veterinary research in six different specialties. In total, 150 randomly chosen clinical studies (25 studies per specialty) published between 2007 and 2019 were evaluated for the breed, sex, neuter status, age, and weight information of the dogs used. Breed information was given for 5.7% of the included animals. Beagles were used 1.9% of the time, which was a less significant role in research than we expected. Information about the sex of the dogs was lacking for 16.2% of the included animals, while age and weight information were missing for 22.7 and 32.7%, respectively. The neuter status was not given in 38.7% of the clinical studies. The results show deficits in the reporting of demographic data for the dogs. The need for an improvement in the documentation and/or reporting of animal signalment is obvious and should be addressed by authors, reviewers, and journal editors in the future.

Abstract

Background: Dogs are widely used in research to answer questions about canine or human conditions. For the latter, research dogs are often used as models, since they are physiologically more similar to humans than other species used in research and they share similar environmental conditions. From a veterinary perspective, research findings are widely based on academic research, and thus are generated under experimental conditions. In that regard, the question arises: do the dogs used for research adequately represent the dog population seen in veterinary practice? It may, for example, be assumed that Beagle dogs are often used as experimental animals. The objective of this study was to evaluate the signalment of dogs used in veterinary research. Furthermore, we aimed to assess other relevant criteria regarding the validity of clinical trials in the context of six different veterinary medicine specialties: cardiology, internal medicine, neurology, orthopaedics, reproduction, and surgery. Methods: A literature search was conducted and 25 studies per specialty were randomly selected. The breed, sex, neuter status, median age, and median weight of the dogs used for clinical studies (n = 150) published between 2007 and 2019 were evaluated. Results: In total, 596,542 dogs were used in the 150 trials. Breed information was given for 33,835 of these dogs (5.7%). Of the latter, 1.9% were Beagles. Nine clinical trials exclusively used Beagles. The most frequently used breeds were German Shepherds (7.3%), Labrador Retrievers (6.7%), and Golden Retrievers (4.7%). The major reporting deficits found were missing breed specification in 25.3% of the articles; missing information about the sex of the dogs in 16.2%; missing age and weight information in 22.7 and 32.7%, respectively; and missing neuter status in 38.7% of the clinical studies. The median sample size was 56 (Q1:29; Q3:365) dogs. Conclusions: The presented project revealed that Beagle dogs represent only a small proportion of dogs in veterinary research. Based on the evaluated publications, it seems that some relevant dog attributes differ between the specialties. The results, however, show deficits in the reporting of demographic data for the dogs. The need for an improvement in the documentation and/or reporting of animal signalment is obvious and should be addressed by authors, reviewers, and journal editors in the future.

Successful treatment of occult hyperadrenocorticism with mitotane but not trilostane in a dog

Background

Occult (or atypical) hyperadrenocorticism (HAC) shows clinical signs and laboratory abnormalities similar to classic hyperadrenocorticism, but normal signs in routine screening tests such as the corticotropin (ACTH) stimulation test and low‐dose dexamethasone suppression test (LDDST). Here, we describe a case of occult HAC in a Yorkshire terrier treated with mitotane.

Case

An 11‐year‐old spayed female presented to the Veterinary Teaching Hospital of Seoul National University because of respiratory distress symptoms, polyphagia, and polydipsia, suggestive of HAC. In abdominal sonography, enlargement of the caudal pole of the left adrenal gland was found, but the cortisol level of post‐ACTH stimulation test was below the cut‐off value, and LDDST was negative. To finalise the diagnosis of occult HAC, 17‐hydroxyprogesterone (17‐OHP) was examined. The concentrations of 17‐OHP (pre‐ and post‐ACTH stimulation) were found to be elevated. As occult HAC was highly suspected, we prescribed trilostane for trial therapy. At first, the clinical signs improved, but they later worsened. We changed medication as trilostane to mitotane, and the symptoms were relieved after mitotane administration.

Conclusion

This is a unique case of occult HAC in which the response to mitotane was better than trilostane.

Adrenocortical Challenge Response and Genomic Analyses in Scottish Terriers With Increased Alkaline Phosphate Activity

Scottish terriers (ST) frequently have increased serum alkaline phosphatase (ALP) of the steroid isoform. Many of these also have high serum concentrations of adrenal sex steroids. The study's objective was to determine the cause of increased sex steroids in ST with increased ALP. Adrenal gland suppression and stimulation were compared by low dose dexamethasone (LDDS), human chorionic gonadotropin (HCG) and adrenocorticotropic hormone (ACTH) response tests. Resting plasma pituitary hormones were measured. Steroidogenesis-related mRNA expression was evaluated in six ST with increased ALP, eight dogs of other breeds with pituitary-dependent hyperadrenocorticism (HAC), and seven normal dogs. The genome-wide association of single nucleotide polymorphisms (SNP) with ALP activity was evaluated in 168 ST. ALP (reference interval 8–70 U/L) was high in all ST (1,054 U/L) and HAC (985 U/L) dogs. All HAC dogs and 2/8 ST had increased cortisol post-ACTH administration. All ST and 2/7 Normal dogs had increased sex steroids post-ACTH. ST and Normal dogs had similar post-challenge adrenal steroid profiles following LDDS and HCG. Surprisingly, mRNA of hydroxysteroid 17-beta dehydrogenase 2 (HSD17B2) was lower in ST and Normal dogs than HAC. HSD17B2 facilities metabolism of sex steroids. A SNP region was identified on chromosome 5 in proximity to HSD17B2 that correlated with increased serum ALP. ST in this study with increased ALP had a normal pituitary-adrenal axis in relationship to glucocorticoids and luteinizing hormone. We speculate the identified SNP and HSD17B2 gene may have a role in the pathogenesis of elevated sex steroids and ALP in ST.

Variability of estradiol concentration in normal dogs

Estradiol concentrations are evaluated in canine serum as part of an adrenal panel used to diagnose atypical Cushing's syndrome and other endocrine abnormalities. Estradiol concentrations are often elevated in dogs without clinical signs of hyperestrogenism, and the significance of this elevation is unknown. The purpose of this study was to estimate the variation in estradiol concentrations in normal dogs. Ten neutered male and female dogs were enrolled in the study. Blood was collected from each dog at 2 h intervals, four times during a given day. This was repeated approximately 1 (week 2) and 5 weeks later (week 6). There was no attempt for a given dog to be started at the exact time or day each week. Results showed that estradiol concentrations ranged from 44.6 to 120.3 pg/mL with a mean of 70.4 pg/mL, which is greater than the upper limit of normal for our laboratory (69 pg/mL). The mean difference between the highest and lowest concentrations for each dog was 28.8 pg/mL, with a range of 12.5-53.5 pg/mL. Mean estradiol concentrations from week 6 (63.2 pg/mL) were significantly lower than those from week 1 (71.4 pg/mL; P=0.015) and week 2 (76.5 pg/mL; P=0.0004). These data show a wide range of variability in estradiol concentration both within and between dogs and that these measurements often exceed the normal ranges established by the laboratory. Therefore, diagnosis of hyperestrogenism or atypical Cushing's syndrome based on increased estradiol concentrations should require compatible clinical presentation of hyperestrogenism together with elevated serum estradiol.