Congenital hypothyroidism of dogs and cats: a review

Clinical and magnetic resonance imaging findings in a French bulldog puppy with genetically confirmed congenital hypothyroidism

A 7-month-old male French bulldog was referred for abnormal mentation and gait. Physical examination revealed a dome shaped calvarium and persistent bregmatic fontanelle. Neurological examination revealed proprioceptive ataxia, pelvic limb paraparesis and strabismus with moderate ventriculomegaly, thinning of the cerebral parenchyma, and widened cerebral sulci on magnetic resonance imaging. Masses were identified in the region of the thyroid, which appeared heterogeneous and hyperintense in T1-weighted and T2-weighted compared with the adjacent muscle signal masses were identified. Radiological diagnosis was hydrocephalus "ex vacuo" and goiter. Blood test revealed abnormally low total thyroxine (TT4), free thyroxine (FT4), and normal thyrotropin concentration. A diagnosis of congenital hypothyroidism was confirmed by positive genetic test for thyroid peroxidase mutation. Thyroxine supplementation treatment rapidly improved clinical signs.

Feline congenital hypothyroidism: a case report

We report a two-month-old male cat weighing 630 grams with congenital hypothyroidism. The main complaints were difficulty defecating for more than three days and prostration. Physical examination revealed a broad, flat face, a short neck, enlarged submandibular lymph nodes, chemosis, mild bilateral mucopurulent ocular discharge, seborrheic coat, with gingival thickening around the upper and lower deciduous incisor teeth with partial eruption. The abdomen was distended due to constipation and right unilateral cryptorchidism. Based on this, feline congenital hypothyroidism was suspected. Hormonal tests (free T4 by equilibrium dialysis of 0.06 ng/dl, total T4 of 0.1 ng/ml and TSH of 4.7 ng/ml) confirmed this. Treatment was started with levothyroxine sodium (5-32.2 µg/kg/day). After 120 days of treatment, there was clinical stabilization. Then the patient underwent orchiectomy of the left and of the right ectopic testicles, and at 380 days of treatment, the thyroid scintigraphy showed intense uptake of the radiopharmaceutical by both thyroid lobes and a significant increase in volume. Clinical evaluation showed weight gain (2.6 kilograms during treatment), improvement in the shape of the skull, and a notable increase in body size. At 17 months of age, hormone values were within the reference limits after administration of levothyroxine sodium (32.2µg/kg/day).

Medical Management of Dental Abnormalities Related to Congenital Hypothyroidism in a Cat

A 5-month-old intact male domestic shorthair cat presenting for routine vaccinations was diagnosed with congenital hypothyroidism. His primary presenting symptom was incomplete dentition with delayed dental eruption. Congenital hypothyroidism was confirmed by baseline thyroxine (T4), free T4, and thyroid-stimulating hormone testing. The cat was treated with oral thyroid hormone supplementation and 16 weeks after initiation of therapy the cat was clinically normal with age-appropriate dentition. No surgical intervention was necessary to achieve normal dental eruption.

Evaluation of Weight Gain, Clinicopathological and Radiographic Changes after Early Diagnosis and Treatment of Congenital Hypothyroidism in Cats

Congenital hypothyroidism is uncommon in cats. This case report describes weight gain, clinicopathological and radiographic changes after early diagnosis and treatment of congenital hypothyroidism in three British shorthair cats’ siblings. Data were assessed at 53 (diagnosis), 83, 185 and 365 days of age. Correlations between serum insulin-like growth factor-1 (IGF-1) and body weight, levothyroxine dose, total thyroxine, and thyroid-stimulating hormone concentrations were evaluated. The body weights of the congenital hypothyroid kittens were compared with those of their two healthy siblings and British shorthair kittens of the same age. At diagnosis, the congenital hypothyroid kittens showed a significantly lower body weight compared to the healthy siblings (p = 0.03). After diagnosis, oral levothyroxine supplementation was started. The difference in body weight was no longer observed after one month of treatment. The clinical signs, clinicopathological and radiographic abnormalities ameliorated after one month of treatment. IGF-1 concentration was significantly positively correlated with body weight (rs = 0.80, p < 0.002). In conclusion, resolution of the clinical signs, achieving a consistent within-breed weight, and improvement of the clinicopathological and radiographic parameters demonstrated the importance of the early diagnosis and treatment of feline congenital hypothyroidism.

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.

METHODS

Case control study of CH-cats and their siblings (2019-2021). Diagnosis was based on low to low-normal serum thyroxine (T4) concentrations, high thyroid-stimulating hormone (TSH) concentrations and clinical signs compatible with CH. We identified the causal variant using Sanger sequencing, genotyping via PCR-RFLP and variant interpretation using ACMG/AMP guidelines.

RESULTS

All CH-cats (5 weeks-8 years) had disproportionate dwarfism. A goiter was not palpable in all. Thyroid scintigraphy with radiopertechnetate showed abnormally high uptake by thyroid glands, whereas scintigraphy with radioiodine showed abnormally low uptake, compatible with a defect in iodine organification by thyroid peroxidase (TPO). All cases were homozygous for TPO variant XM_006930524.4:c.430G>A(p.(Gly144Arg)), while none of the CH-free cats were. All sampled parents were heterozygous for this recessive variant. This variant was found in 15 cat breeds with an estimated allele frequency of 9%.

CONCLUSIONS AND CLINICAL IMPORTANCE

Disproportionate dwarfism, abnormally high TSH and abnormally low to low-normal T4 concentrations are diagnostic for CH in cats. All cases had dyshormonogenesis demonstrated by thyroid scintigraphy. This novel TPO missense variant (not described in humans) causes CH in cats and awareness of it can assist in diagnosis and breeding.

Wellbeing, quality of life, presence of concurrent diseases, and survival times in untreated and treated German Shepherd dogs with dwarfism

BACKGROUND

Pituitary dwarfism (PD) in German Shepherd dogs (GSD) is a rare endocrinopathy. Cause and inheritance of the disease are well characterized, but the overall survival time, presence of concurrent diseases, quality of life (QoL) and influence of different treatment options on those parameters is still not well investigated. The aim of this study was to obtain data regarding the disease pattern of GSD with PD and to investigate the impact of treatment.

METHODS

47 dogs with dwarfism (presumably PD) and 94 unaffected GSD serving as controls were enrolled. Data were collected via a standardized questionnaire, which every owner of a participating dog had completed. Dogs with PD were grouped based on three categories of treatment: Group 1 (untreated), group 2 (treated with levothyroxine), group 3 (treated with thyroxine and progestogens or with growth hormone (GH)). Groups were compared using One-Way-Anova, Kruskal-Wallis test or Wilcoxon-rank-sum test. Categorical analysis was performed using Two-Sample-Chi-Squared-test.

RESULTS

Dogs treated with thyroxine and gestagen or GH were significantly taller and heavier compared to all other dogs with PD. Quality of life was best in dogs with PD treated with thyroxine and similar to unaffected GSD. Treatment increased survival time in dogs with PD independent of the treatment strategy. Dogs receiving thyroxine and progestogens or GH did not develop chronic kidney disease (CKD).

CONCLUSION

GSD with PD should be treated at least for their secondary hypothyroidism to increase survival time. Additional treatment with progestogens or GH improves body size and seems to protect against the occurrence of CKD.

PRESUMPTIVE CONGENITAL HYPOTHYROIDISM IN RED PANDAS (AILURUS FULGENS FULGENS) FROM FOUR SUCCESSIVE LITTERS

High neonatal mortality among red pandas (Ailurus fulgens) challenges the long-term sustainability of the Species Survival Plan population. Congenital hypothyroidism (CH) is a rare condition in domestic animals, typically due to an inherited genetic defect. Nongoitrous CH was presumptively diagnosed in 75% (n = 6/8) of red panda neonates from four successive litters, with a common sire and two closely related dams. Antemortem diagnosis of CH was made in three cubs (n = 3/6) based on elevated thyroid stimulating hormone and decreased free thyroxine and total thyroxine levels. Affected cubs also had suggestive clinical signs, which included delayed growth with cretinous dwarf appearance, atonic bladder, delayed gastrointestinal motility, hypercholesterolemia, and hypocalcemia. With sodium levothyroxine therapy, two of the three cubs developed into normal adult red pandas in terms of body size, appearance, and behavior. On necropsy cubs (n = 4) were small with varying degrees of cretin dwarf appearance and hypoplastic thyroids with reduced to no colloid in follicles. These cases demonstrate the importance of collecting thyroid tissue, (or proximal trachea/larynx if gross visualization not possible), in neonates for histopathology. Further investigation into the role of thyroid disease in neonatal red panda mortality is warranted.

Congenital goiter with areas of signet ring cell differentiation in a juvenile giraffe: a very rare entity

BACKGROUND

Congenital goiter is a common thyroid metabolic disorder characterized by low levels of thyroid hormone, subsequent secretion of excess thyroid-stimulating hormone (TSH) from the pituitary gland, and compensatory hyperplasia of the glands. The presence of signet ring cells (SRCs) does not provide sufficient evidence for the diagnosis of a thyroid tumor, making histopathological diagnosis challenging. In addition, SRCs can also appear in congenital goiter. Therefore, a comprehensive diagnosis of congenital goiter is warranted based on clinical symptoms, autopsy, histopathology, and laboratory examination.

CASE PRESENTATION

A juvenile giraffe at the Ordos Zoo in Ordos presented with symptoms of loss of appetite, serious salivation, and slow growth rate since birth. Its height and weight were significantly lower than those of other giraffes of the same age. The animal ultimately died at 17 months of age. Autopsy revelaed that the thyroids were hard, with an uneven surface and with the presence of many small raised follicles, and dense in cross-section. Other organs were visibly atrophic. Histopathologically, diffuse follicles were irregular in size and shape in the hyperplastic goiter. Some follicles were collapsed due to lack of colloids. The follicles were lined by single or multiple layers of hyperplastic follicular cells (HFCs), some of which were exfoliated in the lumen. The HFCs were either cuboidal with eosinophilic cytoplasm and many red small granules or showed SRC differentiation, with nuclei pressed to one edge of the cell and distorted by cytoplasmic mucin that appeared as a single clear vacuole HFCs and as a foamy, multivesicular cytoplasmic material in others. Scattered necrosis of myocardial cells and hepatocytes, cerebral hemorrhage, necrosis of intestinal villi, and obvious atrophy of organs were also observed. Immunohistochemical tests were strongly positive for thyroglobulin and thyroid transcription factor-1 (TTF-1) in the cytoplasm of HFCs.

CONCLUSIONS

Here we present a case of congenital goiter with areas of SRC differentiation in the thyroid of a juvenile giraffe.

Cluster of cases of congenital feline goitrous hypothyroidism in a single hospital

OBJECTIVES

To describe the clinicopathological findings and outcomes of cases of feline congenital hypothyroidism diagnosed in a single veterinary hospital in Santiago, Chile.

MATERIALS AND METHODS

Medical records were searched for cases of congenital hypothyroidism over an 18-month period. Inclusion criteria were a diagnosis of congenital hypothyroidism based on consistent historical and clinical findings, a low or low-normal serum total T4 and elevated serum canine TSH (cTSH).

RESULTS

Six unrelated cats ranging in age from 4 to 19 months met the inclusion criteria. The most common historical signs were small stature and lethargy. All cats had disproportionate dwarfism, delayed tooth eruption, retained deciduous teeth, bilateral palpable goitres and low rectal temperatures. Other findings were bradycardia, obesity, poor hair coat and focal alopecia on the ventral aspects of the elbows and hocks. In all cases, cTSH was markedly elevated. Sequential changes noted after the initiation of therapy included normal T4 after 6 weeks, improved hair coat and increased physical activity by 8 weeks, normal cTSH by 10 weeks and normal physical appearance and dentition after 4 months. Goitres shrank markedly but remained palpable. Hypothyroidism was well managed clinically in all cases 2 years after diagnosis except for one cat that died of unrelated causes.

CLINICAL SIGNIFICANCE

This is the first report to describe a cluster of congenital hypothyroidism cases in non-related cats that were presented over a short period of time. Growth defects resolve with treatment, even in cats diagnosed after puberty. Larger, prospective multi-centre studies are warranted to determine the incidence of congenital hypothyroidism in cats.

Whole-genome genotyping and resequencing reveal the association of a deletion in the complex interferon alpha gene cluster with hypothyroidism in dogs

Background

Hypothyroidism is a common complex endocrinopathy that typically has an autoimmune etiology, and it affects both humans and dogs. Genetic and environmental factors are both known to play important roles in the disease development. In this study, we sought to identify the genetic risk factors potentially involved in the susceptibility to the disease in the high-risk Giant Schnauzer dog breed.

Results

By employing genome-wide association followed by fine-mapping (top variant p-value = 5.7 × 10^− 6), integrated with whole-genome resequencing and copy number variation analysis, we detected a ~ 8.9 kbp deletion strongly associated (p-value = 0.0001) with protection against development of hypothyroidism. The deletion is located between two predicted Interferon alpha (IFNA) genes and it may eliminate functional elements potentially involved in the transcriptional regulation of these genes. Remarkably, type I IFNs have been extensively associated to human autoimmune hypothyroidism and general autoimmunity. Nonetheless, the extreme genomic complexity of the associated region on CFA11 warrants further long-read sequencing and annotation efforts in order to ascribe functions to the identified deletion and to characterize the canine IFNA gene cluster in more detail.

Conclusions

Our results expand the current knowledge on genetic determinants of canine hypothyroidism by revealing a significant link with the human counterpart disease, potentially translating into better diagnostic tools across species, and may contribute to improved canine breeding strategies.

Congenital dyshormonogenic hypothyroidism with goiter caused by a sodium/iodide symporter (SLC5A5) mutation in a family of Shih-Tzu dogs

An iodide transport defect (ITD) in the thyroid gland was determined to cause congenital dyshormonogenic hypothyroidism with goiter (CDHG) in 2 members of a family of Shih-Tzu dogs. Strikingly, both dogs were also diagnosed with dilated cardiomyopathy at 24 and 1.5 mo of age. The only sign of hypothyroidism was a moderate growth delay in the adult dog. The ITD was recognized by the absence of uptake of technetium-99m in the salivary glands (sg) and goiter observed by scintigraphy. In the same scan, radiopharmaceutical uptake was found in the anterior mediastinum of both dogs and in the right axillary lymph node in the oldest dog. A follicular thyroid carcinoma was diagnosed by histopathology after thyroidectomy of the older dog. An adenomatous goiter with ectopic thyroid tissue, and degenerative changes in myocardium were the findings after necropsy in the youngest dog. A homozygous mutation of the intron 9 splice acceptor site of SLC5A5 gene, encoding the sodium/iodine symporter (NIS), was found in the DNA of one of the affected dogs. The mutation was a single base transition of guanine > adenine (G > A) at position 45,024,672 of dog chromosome 20 (CFA20). Five of eight healthy dogs, including both parents of one of the dogs exhibiting CDHG, were heterozygous A/G, and the other 3 were homozygous for the wild-type allele G/G. No sequence variant was found in thyroid peroxidase of the affected dog. Congenital dyshormonogenic hypothyroidism with goiter in this family is an autosomal recessive trait. Our findings are the first evidence of an SLC5A5 mutation in dogs and establish a new genetic cause of CDHG.

Congenital Feline Hypothyroidism With Partially Erupted Adult Dentition in a 10-Month-Old Male Neutered Domestic Shorthair Cat: A Case Report

Congenital feline hypothyroidism was diagnosed in a 10-month-old kitten. The kitten appeared to have disproportionate dwarfism, with the clinical signs of incompletely erupted permanent dentition covered by thickened gingival tissue, short stature, a broad, flattened face, short neck, pendulous abdomen, kitten-like hair coat, and goiter. Hypothyroidism was confirmed with baseline T4, freeT4, and thyroid-stimulating hormone testing. The kitten was treated with thyroid hormone supplementation and monitored. The kitten appeared clinically like a normal healthy cat at 22 months of age on thyroid supplementation.

Development of the independent function of fetal thyroid glands in the dog in connection with iodothyronine concentrations in pregnant bitches, fetal fluids, and fetal serum

Thyroxine (T₄) and triiodothyronine (T₃) concentrations in pregnant and nonpregnant bitches were measured. The allantoic and amniotic fluid samples were collected separately in the third week of pregnancy, and fetal blood samples were collected in the fourth week of pregnancy. There was no difference between T₄ results in the pregnant and nonpregnant animals, but the measured serum concentrations exceeded the healthy range for normal adults. Serum T₄ concentrations were lower in the fetus than those in adults (P < 0.01). Fetal T₄ concentrations continuously increased and reached 13.38 ± 6.19 nmol/L before birth. The fetal serum T₄ concentrations were lower than the T₄ concentrations in allantoic and amniotic fluid until the seventh week, and the fetal serum T₃ concentrations were lower than those in fetal fluids throughout the pregnancy (P < 0.01). Maximum T₃ concentrations in allantoic and amniotic fluid exceeded the concentrations in the fetal and maternal serum. It is conceivable that the considerable differences between maternal and fetal serum T₄ concentrations in healthy animals are explained by the T₄ impermeability of the placenta. Extremely high maternal T₄ (193.5 nmol/L) in 1 bitch was associated with T₄ concentrations under the detection limit in the fetal fluids and serum suggesting an inhibitory effect. The T₄ concentrations in all the fetal fluids and serum were under the detectable concentration that can be defined by 3.0 nmol/L in that bitch. We have demonstrated that fetal thyroid glands start functioning independently at the same time as thyroid cell formation in the dog, but the overproduction of maternal T₄ may have a suppressive effect on fetal iodothyronine production.

Primary goitrous hypothyroidism in a young adult domestic longhair cat: diagnosis and treatment monitoring

Case summary

Primary goitrous hypothyroidism was diagnosed in a 12-month-old cat examined because of small stature, mental dullness, severe lethargy, generalized weakness and gait abnormalities. Radiographs of the long bones and spine revealed delayed epiphyseal ossification and epiphyseal dysgenesis. Diagnosis of primary hypothyroidism was confirmed by low serum concentrations of total and free thyroxine (T4) with high thyroid-stimulating hormone (TSH) concentrations. Thyroid scintigraphy revealed severe enlargement of both thyroid lobes, as evidenced by a seven-fold increase in calculated thyroid volume above the reference interval. In addition, this bilateral goiter had an extremely high radionuclide uptake, about 10-fold higher than the normal feline thyroid gland. Treatment with twice-daily levothyroxine (L-T4), administered on an empty stomach, resulted in increased alertness, playfulness, strength and improvement in gait, as well as an increase in body length and weight. L-T4 replacement also led to normalization of serum thyroid hormone and TSH concentrations, and complete resolution of goiter.

Relevance and novel information

Spontaneous hypothyroidism is rarely reported in cats, with congenital hypothyroidism in kittens diagnosed most frequently. Despite the fact that this cat was a young adult, it likely had a form of congenital hypothyroidism caused by dyshormonogenesis (defect in thyroid hormone synthesis) that led to compensatory development of goiter. In hypothyroid cats, treatment with L-T4 is best given twice daily on an empty stomach to ensure adequate absorption. Normalization of serum TSH and shrinkage of goiter, as well as improvement in clinical signs, is the goal of treatment for cats with goitrous hypothyroidism.

Molecular Genetic Characterization of Thyroid Dyshormonogenesis in a French Bulldog

Background

A case of congenital hypothyroidism with goiter (CHG) in a juvenile French bulldog was identified and hypothesized to be caused by dyshormonogenesis of genetic etiology.

Objectives

To describe case management, unusual phenotypic aspects, and a CHG‐causing mutation in a French bulldog.

Animals

Thyroid tissue and blood from a CHG‐affected French bulldog and 4 normal control dogs and buccal brush samples of 125 French bulldogs were studied.

Methods

Standard clinical assessment and laboratory tests were applied. Thyroid peroxidase (TPO) iodide oxidation activity was measured in vitro, and TPO protein was assessed on Western blots. Thyroid peroxidase exons and flanking splice sites were amplified from genomic DNA and sequenced. Thyroid peroxidase cDNA was amplified from thyroid RNA and sequenced.

Results

At 9 months of age, the affected dog had signs of cretinism, but near‐normal skeletal maturation. The enlarged thyroid glands exhibited noninflammatory fibrosis and aberrant follicular organization. Thyroid peroxidase activity and immunocrossreactive protein were undetectable. There was a T>C mutation of the intron 12 splice donor consensus that caused abnormally spliced mRNA, consistent with absent TPO function. The mutant allele was not observed in 125 clinically normal French bulldogs.

Conclusions

Presumptive CHG in a French bulldog with unusual clinical presentation is described. Genetic etiology was confirmed by identifying the underlying TPO mutation.

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.

A thyroid peroxidase (TPO) mutation in dogs reveals a canid-specific gene structure

Congenital hypothyroidism with goiter (CHG) occurring as an autosomal recessive disorder is typically due to a defect of thyroid hormone synthesis (aka dyshormonogenesis). Thyroid peroxidase (TPO) is a multifunctional, heme-containing enzyme whose activity is required, and several inactivating TPO mutations causing CHG in humans and dogs have been described. Recently, two half-sib Spanish water dog (SWD) pups were diagnosed with CHG based on clinical signs, endocrine testing, and thyroid histology. TPO enzyme activity was absent, and immuno-cross-reactive TPO was undetectable in affected-dog thyroid tissue. A single guanosine insertion was observed in the first exon of the affected-dog TPO cDNA at a site not previously thought to be within the coding sequence. The insertion allele segregated with the deduced disease allele in the SWD breed and was not observed in unrelated dogs of various breeds. Comparison of the insertion site (an 8-nt poly-G tract) with the orthologous sequences of other mammalian reference genomes revealed that the octa-G tract obliterated the intron 1 splice acceptor site and the exon 2 translation initiation codon found at that position in other species. An in-frame ATG in strong Kozak consensus context was observed in the normal dog sequence 12 codons 5' of the usual mammalian start site, suggesting that dogs have lost the noncoding exon 1 demonstrated in human and mouse. A survey of TPO sequences in other carnivore species indicates that the poly-G tract necessitating an alternative translation initiation site is a canid-specific feature.

Congenital hypothyroidism with goiter in Tenterfield terriers

BACKGROUND

A cluster of cases of congenital hypothyroidism with goiter (CHG) in Tenterfield Terriers was identified and hypothesized to be dyshormonogenesis of genetic etiology with autosomal recessive inheritance.

OBJECTIVES

To describe the phenotype, thyroid histopathology, biochemistry, mode of inheritance, and causal mutation of CHG in Tenterfield Terriers.

ANIMALS

Thyroid tissue from 1 CHG-affected Tenterfield Terriers, 2 affected Toy Fox Terriers, and 7 normal control dogs. Genomic DNA from blood or buccal brushings of 114 additional Tenterfield Terriers.

METHODS

Biochemical and genetic segregation analysis of functional gene candidates in a Tenterfield Terrier kindred. Thyroid peroxidase (TPO) iodide oxidation activity was measured, and TPO protein and SDS-resistant thyroglobulin aggregation were assessed on western blots. TPO cDNA was amplified from thyroid RNA and sequenced. Exons and flanking splice sites were amplified from genomic DNA and sequenced. Variant TPO allele segregation was assessed by restriction enzyme digestion of PCR products.

RESULTS

Thyroid from an affected pup had lesions consistent with dyshormonogenesis. TPO activity was absent, but normal sized immunocrossreactive TPO protein was present. Affected dog cDNA and genomic sequences revealed a homozygous TPO missense mutation in exon 9 (R593W) that was heterozygous in all obligate carriers and in 31% of other clinically normal Tenterfield Terriers.

CONCLUSIONS

The mutation underlying CHG in Tenterfield Terriers was identified, and a convenient carrier test made available for screening Tenterfield Terriers used for breeding.