Page 2627 - Cote clinical veterinary advisor dogs and cats 4th

1338 Estradiol/Estrogen, Serum Levels Ethylene Glycol Testing

Estradiol/Estrogen, Serum Levels
VetBooks.ir Definition

exploratory surgery is recommended (persistent
Hormone synthesized and secreted by develop- concentrations < 12-15 pg/mL. Estradiol increases above 2.5 ng/mL 5-7 days later,
concentrations > 20 pg/mL typically accom-
ing ovarian follicles pany follicular activity (follicular phase of the ovarian tissue). This test is not used in dogs.
feline cycle averages 7.0-7.7 days, depending
Physiology on whether coitus is experienced and whether Important Interspecies Differences
Dogs: Proestrus is under the influence of pro- ovulation is induced). Day 1 of the follicular • Cats are induced ovulators and are seasonally
gressively increasing circulating concentrations phase of estrus typically is associated with an polyestrous.
of estradiol, which is produced by the develop- estradiol concentration ≈25 pg/mL; at day 3 • Dogs are spontaneous ovulators and have a
ing ovarian follicles. A rising estradiol level it is ≈45 pg/mL, at day 5 it is ≈50 pg/mL or typical interestrus interval of 7-12 months.
correlates with development of marked changes above, at day 7 it is ≈20-25 pg/mL, and by
in the vaginal mucosa, vulva, and uterus. Serum day 8 it has returned to ≈10 pg/mL. Lab Artifacts
estradiol concentrations start to increase just Increased values in hemolyzed or lipemic
before proestrus becomes clinically detectable. Reference Interval samples; gel from serum separator tubes causes
Estradiol concentrations above 25 pg/mL are Dog: baseline during anestrus is 5-15 pg/mL. variable interference
typical of early proestrus, and concentrations Unit conversion formula: 1 pg/mL × 3.67 =
greater than 60-70 pg/dL are typical of late 1 pmol/L Specimen Collection and Handling
proestrus. Peak estradiol serum concentrations Serum (2 mL minimum) collected in a red
are reached 24-48 hours before the end of Causes of Abnormally High Levels top tube (do not use serum separator tubes).
proestrus before standing heat (estrus). Male • Dog/intact: mid to late proestrus Analyte is stable in serum sample maintained
dogs with Sertoli cell tumors and male feminiza- • Cat/intact: midfollicular phase of estrus cycle at 2°C-4°C for up to 48 hours. Specimens
tion syndrome have increased production of • Spayed/suspected spayed dog or cat: ovarian should be frozen if analysis interval is longer.
estrogens by testicular tumor cells, or increased remnant
androgenous hormone conversion to estrogens Relative Cost: $$
by metabolic tissues (e.g., liver, neural tissue) Causes of Abnormally Low Levels
or testicular cells, or normal estrogen levels are • Ovariectomy Pearls
concurrent with decreased androgen levels. In • Measurement during anestrus or diestrus • Antimullarian hormone is the preferred test
male dogs with Sertoli cell tumors, estrogens are phase of cycle for assessing for ovarian remnants or spay
typically not measured. Typically, the feminizing status.
syndrome is recognized through overt clinical Next Diagnostic Steps to Consider • Luteinizing hormone may also be used
signs, and the underlying tumor is surgically if Levels Are High to determine spay status in a patient not
removed without serologic testing. In suspected ovariectomized cats administer currently showing signs of heat.
Cats: Anestrus and interestrus periods hCG to cause luteolysis of follicles; check
typically are associated with estradiol serum for increasing progesterone. If progesterone AUTHOR & EDITOR: Lois Roth-Johnson, DVM, PhD,
DACVP

Ethylene Glycol Testing

Definition • VetSpec Ethylene Glycol Qualitative Reagent Urine calcium oxalate monohydrate crystals may
Point-of-care/cage-side test kits for the diagnosis Test Kit (Catachem, Inc.): reported as be present in the first few hours of toxicities.
of ethylene glycol (antifreeze) toxicity negative or positive (quantified at ≈5 mg/ See p. 314.
dL, ≈150 mg/dL, or ≥ 300 mg/dL)
Physiology Causes of Abnormally Low Levels
Ethylene glycol (antifreeze) is not toxic in its Causes of Abnormally High Levels Ethylene glycol is rapidly metabolized and
pure state, but the breakdown products from Consumption of ethylene glycol (usually within cleared from the bloodstream; test is negative
oxidation within the kidney and the liver result 12 hours) if exposure has been > 12-18 hours.
in glycolic acid and oxalate accumulation and
subsequent nephrotoxicosis and metabolic Next Diagnostic Steps to Consider Next Diagnostic Steps to Consider
acidosis. The available test kits only detect if Levels Are High if Levels Are Low
plasma ethylene glycol concentration, not the Ethylene glycol toxicity results in marked If clinical history suggests intoxication, evaluate
nephrotoxic metabolites. acid-base, electrolyte, and osmolality derange- renal parameters, electrolytes, and acid-base
ments along with acute kidney injury. Blood status. Determine serum levels of metabolites
Reference Interval gas and electrolyte panels to identify a marked (glycolic acid).
• Kacey Ethylene Glycol Test Strips (Kacey, metabolic acidosis, electrolyte derangements
Inc.): reported as negative, 20, 50, or 75 mg/ (hypochloremia/hyperkalemia), and possible Important Interspecies Differences
dL. Positive result is ≥ 20 mg/dL (cat) and hypocalcemia. Renal panels and urinalysis for Both tests are approved for dogs and cats.
≥ 50 mg/dL (dog). evidence of acute kidney injury (azotemia).

www.ExpertConsult.com