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Testosterone Thyroglobulin Antibody (TgAA) 1385

Testosterone
VetBooks.ir Definition

primary infertility disorder or could be seen
Testosterone is an anabolic steroid hormone concentration can fluctuate in normal intact testosterone concentration may indicate a
males, and accordingly, sometimes a baseline
derived from cholesterol. Most often measured sample is collected and compared with a second with the presence of a Sertoli cell tumor.
to differentiate castrated males from cryptorchid sample following administration of human
males, but is also included on adrenal sex chorionic gonadotropin (hCG) or gonadotropin Next Diagnostic Steps to Consider
hormone panels releasing hormone (GnRH); either should if Levels are Low
increase testosterone concentration. In intact male, consider assessment of other sex
Physiology hormones and evaluation of the patient for the
• Testosterone is an androgen and accordingly Causes of Abnormally High Levels presence of a Sertoli cell tumor.
has key roles in male gonadal development In a male patient who is thought to be castrated,
and fertility. Testicular Leydig/interstitial increased testosterone concentration suggests Drug Effects
cells in intact males produce the majority of the presence of remaining Leydig/interstitial Administration of testosterone compounds will
testosterone, so castrated males and females cells (cryptorchid or remnant testicular tissue). increase results.
are expected to have very low testosterone Slightly increased concentration may require
concentrations. additional testing for clarification (hCG stimu- Lab Artifacts
• Aberrations in steroidal hormone enzymes lation testing, measurement of antimullerian Serum separator tubes may interfere with results;
can occur in adrenal cortical neoplasms, hormone). use plain red top tubes for blood collection.
potentially leading to increased adrenal
testosterone production. Next Diagnostic Steps to Consider Specimen Collection and Handling
if Levels are High Collect blood in a red top tube, and harvest
Reference Interval Abdominal imaging to locate cryptorchid serum. Submit serum on ice, ideally overnight.
Varies by laboratory. One example states testicle(s).
that intact male dogs and cats should have Relative Cost: $$
testosterone concentrations of > 0.1 ng/mL, Causes of Abnormally Low Levels
whereas castrated males and females should have Low concentration is expected in castrated AUTHOR: Angela Royal, MS, DVM, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
concentrations < 0.01 ng/mL. Basal testosterone males and females. In an intact male, decreased

Thyroglobulin Antibody (TgAA)

Definition Causes of Abnormally High Levels Lab Artifacts Laboratory Tests
Autoantibodies directed at thyroglobulin, associ- Increased TgAA results indicate the presence Nonspecific binding of immunoglobulins
ated with canine autoimmune thyroiditis. TgAA of autoimmune thyroiditis, or rarely may be can falsely increase TgAA results; however,
is generally included as part of a thyroid testing associated with thyroid neoplasia. nonspecific binding can be quantified and
panel rather than measured as a stand-alone test. TgAA results adjusted accordingly to negate
Next Diagnostic Steps to Consider this interference.
Physiology if Levels are High
Lymphocytes involved in autoimmune TgAA is generally included as part of a Specimen Collection and Handling
thyroiditis can produce antibodies directed thyroid testing panel. Increased TgAA should Collect blood into a plain red top tube or
at a variety of epitopes along thyroglobulin be interpreted in light of the other tests on serum separator tube, allow to clot, centrifuge,
molecules. Collectively these antibodies are the panel to determine whether the patient is and remove serum. Freeze serum (or keep
termed TgAA. The presence of circulating truly hypothyroid. Patients with high TgAA refrigerated if shipping the day of collection)
TgAA indicates autoimmune thyroiditis is but normal thyroid hormone status should and submit serum alone, on ice, overnight. In
present, but does not alone predict whether be rechecked in the future for the potential general, gross hemolysis or lipemia should be
the patient has hypothyroidism. In some cases, emergence of hypothyroidism. avoided.
detectable TgAA may be found with normal
thyroid hormone and TSH concentrations. A Next Diagnostic Steps to Consider Relative Cost: $$
subset of these patients will proceed to clinical if Levels are Low
hypothyroidism. OFA Thyroid Registry certifi- TgAA will remain within normal limits in Pearls
cation requires normal TgAA results (along with some hypothyroid dogs. The remainder of • Increased TgAA is a common finding in
fT 4 and TSH results) as autoimmune thyroiditis the panel results should be used to decide hypothyroid dogs and indicates autoimmune
is a heritable condition. whether hypothyroidism is still likely for the thyroiditis is present.
patient. Low TgAA also does not entirely rule • Not all dogs with hypothyroidism will have
Reference Interval out the possibility of autoimmune thyroiditis. increased TgAA.
Will be provided by your laboratory. Example: • Increased TgAA can be seen in patients
0%-35%, with results interpreted as negative, Important Interspecies Differences without hypothyroidism.
positive, or inconclusive. Measured in dogs only

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