di Cristina Di Palma • Medico Veterinario
di Cristina Di Palma
Medico Veterinario
La tiroidite autoimmune è la causa più comune di ipotiroidismo primario nel cane. La patologia ha una eta’ di insorgenza variabile, ma tende a conclamarsi tra i 2 e i 5 anni di età: fino a quando la disfunzione tiroidea non si conclama clinicamente i cani appaiono in salute, poiché la formazione degli autoanticorpi anti tireoglobulina precede la manifestazione clinica. Questo è il motivo per cui fattrici e stalloni vanno periodicamente testati almeno ogni 1-2 anni: lo sviluppo di autoanticorpi antitireoglobulina indica che il cane ha la forma genetica della patologia tiroidea. L’incidenza di falsi positivi non è così frequente nei cani testati, al contrario un soggetto i cui test sono risultati negativi non è detto che in futuro non svilupperà la forma di tiroidite autoimmune.
– f-T4 (free T4): tiroxina libera è il gold standard per la determinazione della produzione tiroidea e la disponibilità cellulare della tiroxina. In caso di tiroidite autoimmune questo valore è basso.
– cTSH (ormone tireo stimolante):indica il livello di ormone che stimola la tiroide a produrre tiroxina (T4). In caso di tiroidite autoimmune il valore atteso è molto alto.
– TgAA (auto anticorpi anti tireoglobulina) se positivo questo test indica la presenza di una tiroidite auto immune.
Eseguire lo screening tiroideo su fattrici e stalloni sarebbe di aiuto agli allevatori nell’impostazione del loro programma di riproduzione al fine di ridurre l’incidenza di patologie tiroidee immunomediate nella discendenza.
Normal
FT4 within normal range
cTSH within normal range
TgAA is negative
Positive autoimmune thyroiditis
FT4 less than normal range
cTSH greater than normal range
TgAA is positive
Positive compensative autoimmune thyroiditis
FT4 is within normal range
cTSH is greater than or equal to normal range
TgAA is positive
Idiopathically reduced thyroid function
FT4 is less than normal range
cTSH greater than normal rang
TgAA is negative
Purpose
To identify those dogs that are phenotypically normal for breeding programs and to gather data on the genetic disease autoimmune thyroiditis.
Examination and Classification
Each dog is to be examined by an attending veterinarian and have a serum sample sent to an OFA approved laboratory for testing according to the enclosed application and general information instructions. The laboratory fee will be determined by the approved laboratory. All OFA forms and the OFA fee are submitted with the sample to the approved lab. Check with the referral laboratory for special sample handling and tests for registry purposes.
Certification
A breed database number of will be issued to all dogs found to be normal at 12 months of age. Ages will be used in the certification process since the classification can change as the dog ages and the autoimmune disease progresses. It is recommended that reexamination occur at ages 2,3,4,6, and 8 years.
Preliminary Evaluation
Evaluation of dogs under 12 months of age can be performed for private use of the owner since the few dogs are already positive at that age. However, certification will not be possible at that age.
Dogs with Autoimmune Thyroiditis
All data, whether normal or abnormal is to be submitted for purposes of completeness. There is no OFA fee for entering an abnormal evaluation of the thyroid into the data bank. Information on results determined to be positive or equivocal will not be made public without explicit written permission of the owner.
Thyroid Abnormalities
Thyroid abnormalities fall into several categories—two types will be defined by the registry.
Autoimmune Thyroiditis
Idiopathically Reduced Thyroid Function
Autoimme thyroiditis is known to be heritable.
Equivocal Results
Those dogs with laboratory results that are questionable, therefore not definitive, will be considered as equivocal. It is recommended that the test the repeated in three to six months.
The veterinarian or owner must obtain the “Application for Thyroid Database.
The veterinarian and owner must complete their respective portions of the form.
A check for $15.00 payable to the OFA and the completed OFA form must accompany the specimen.
The veterinarian should request the “OFA Thyroid Panel.”
Two milliliters (2mL) of serum are needed for testing. The serum sample must be from freshly collected blood. Use a plain “red-top” tube for blood collection. Do not use a serum separator tube with clot additives or any other type of plasma collection tube. After collection, place the blood sample in the refrigerator for 60 to 90 minutes to allow clotting. Centrifuge, collect the serum, and transfer to a plain plastic or glass tube suitable for shipping. Clearly label the sample with the owner’s name, animal’s identification, date of blood collections, and “OFA Thyroid Panel.” If the specimen is to be stored for more than 12 hours prior to shipping, frozen storage is recommended.
Ship to the chosen lab address via an overnight courier service. It is recommended that all specimens be packaged properly and shipped so they are received either chilled or frozen. Serum samples arriving unchilled or at room temperature within 48 hours of the collection date will be accepted. However, samples arriving after this time must be received either chilled or frozen in order to be accepted for registry testing. Contact the laboratory if you have any questions or further instructions are needed.
Please do not submit whole blood, clotted blood, or plasma.
Severely lipemic or hemolyzed specimens are also unacceptable.
Female dogs should not be tested during an estrus cycle.
The date of last routine vaccination should be noted on the OFA application.
Test results will be mailed or faxed only to the submitting veterinarian and the OFA. Results will not be available from the laboratory by telephone. The OFA will send a report to the owner.
Associazione Specializzata
di Razza riconosciuta dall’Ente
Nazionale della Cinofilia Italiana
Associazione Specializzata di Razza riconosciuta dall’Ente Nazionale della Cinofilia Italiana
Rhodesian Ridgeback Club d’Italia ©2022 – Sede legale: c/o ENCI – V.le Corsica, 20 – 20137 Milano – C.F. 97209800156
Rhodesian Ridgeback Club d’Italia ©2022
Sede legale: c/o ENCI – V.le Corsica, 20
20137 Milano
C.F. 97209800156