Frequently Asked Questions

UC Davis Clinical Endocrinology Lab Frequently Asked Questions

Biology of testing


GCT panels:

  • Can a mare stay on ReguMate/Altrenogest/Depo-Provera when testing for a GCT?
  • Yes. None of the synthetic progestin therapies will interfere with analysis of anti-Mϋllerian hormone (AMH), inhibin-B or testosterone. In fact, none of the synthetic progestins named above will interfere (cross-react) in our immuno-assay for progesterone.
  • Will it affect the GCT panel if we switch the mare to a longer lasting progesterone?
  • No. Long acting progesterone (or synthetic progestin) will not affect analysis of any of the analytes in the GCT panel (AMH, inhibin-B or testosterone).

Pregnancy determination:

  • How many days pregnant does my mare need to be for estrone sulfate testing?
  • Our current guidelines suggest that testing is effective if mares are greater than 45 days for standard breeds but greater than 80 days for mini breeds. However, no test is perfect and estrone sulphate starts to increase around those times. Therefore, the chances of obtaining a false negative result decrease the longer after 45 days for standard breeds or 80 days for minis the sample is drawn.
  • How pregnant does my camelid need to be for progesterone testing as an indirect determination of pregnancy?
  • Assuming males are fertile and mating induces ovulation and therefore pregnancy, progesterone is elevated typically >2ng/ml by day 5. If the mating is successful at inducing ovulation but does not result in pregnancy (sterile mating), progesterone will decline by day 10-15 post-mating. Therefore, our current recommendation is to draw samples after 20 days post-mating (our current range is greater than 20 days pregnant)
  • How accurate is the estrone sulfate test for equine pregnancy?
  • No test is perfect, and pregnancies can fail and abort at any stage from a number of causes. Estrone sulphate secretion by the mare’s ovary is stimulated by hormone secretion (equine chorionic gonadotropin, eCG) from the early placenta. Then the placenta itself secretes estrone sulphate stimulated by the growing fetus, with a second more dramatic rise from about 90 days of gestation, peaking at about 7 months of gestation. However, if the pregnancy is lost, estrone sulphate secretion ceases and it disappears from the circulation within days. Therefore, a positive test indicating a viable pregnancy at the time of sampling does not guarantee that it will stay elevated and that a foal will be delivered at term. The accuracy of estrone sulphate as a test for pregnancy is affected by failed pregnancies and we do not have accurate statistics on this.
  • Can you use estrone sulfate to determine pregnancy in donkeys, mules or zebras? Are the reference ranges the same as for horses?
  • We have not had the opportunity to establish reference ranges for pregnancy in either donkeys or zebras but we suspect that donkey ranges for standard and mini types will likely be similar to those for standard and mini horses. I can recall one zebra sample we got that looked positive and several that did not but the outcome was not reported (to me anyway), so whether or not that one mare dropped a foal, and therefore was indeed pregnant at the time of sampling, is an unknown at this point.

Feline/Canine AMH:

  • Does the dog or cat need to be showing signs of estrus when I draw the sample for ovarian remnant testing?
  • No. In fact, AMH concentrations change during the canine estrous cycle and are often lower when the females are showing signs of estrus [1]. This means that a sample drawn while a female is showing signs of estrus is more likely to be falsely negative on an AMH test. However, progesterone is increasing as AMH is decreasing when females are showing signs of estrus and so including progesterone can confirm the presence of ovarian tissue when an AMH test result might be negative [2].
  • How accurate is the canine/feline AMH test for detecting ovarian remnants?
  • Again, no test is perfect and the diagnosis of ovarian remnant is greatly enhanced if there is a history of repeated episodes of apparent estrus at about 6 month intervals. However, ORS was evaluated by Cornell AHDC who reported on 47 cats and 56 dogs that were investigated for ORS. Of these, 29 animals underwent exploratory surgery, and 28 were found to have a remnant. There were 3 false negatives in dogs out of 56 dog samples. Of these, all had elevated progesterone. In addition, 2 of 4 dogs that tested as “inconclusive” went to surgery, and both had remnant. [2]

General:

  • Do you perform testing on any other species (i.e. pigs, cows, goats, sheep, exotic species, etc.)?
  • We can often perform testing on different species, however reference ranges may not be available. Please contact the lab with specific questions regarding test cross-reactivity. Equine AMH cross reacts well with sheep, but only has one third the reactivity in cows, and no reactivity in goats.  Equine inhibin B cross reacts with goats. Testosterone works across all species, but we only have reference ranges for males of all species, and equine females. Estrone sulfate works well for pregnancy detection in mares and goats. It may no be accurate in other species.

Sample Handling:

  • What are the sample handling and shipping guidelines?
  • Do not send whole or clotted blood. Please send serum only. Blood contains active enzymes which may affect the results of endocrine tests. For the protein hormones: inhibin and AMH, and panels containing AMH, please separate the serum and ship priority overnight on an ice pack, to arrive by approximately 10:30 a.m. A serum sample that is left in the refrigerator for more than 2 days, or shipped over the weekend may have falsely elevated AMH levels. Steroid hormones: testosterone, DHP, progesterone, estrone sulfate, are more stable. However, they may be degraded by poor handling conditions, shipment in serum separator tubes, or as whole or clotted blood. For the best test results, you must submit the best quality samples.
  • Is it OK to use serum separator tubes?
  • We don’t recommend serum separator tubes, because limited data from canine/feline AMH, and progesterone samples suggest that they may marginally increase the amount of analyte, especially if shipped or stored in the tube. We don’t have data on whether serum separator tubes affect all of the hormone tests. Therefore, we just issue a blanket recommendation that they are not used to store or ship blood. IF a serum separator tube is used, then the best practice is to spin, and remove the serum to a new tube as soon as possible (within a few hours).

Shipping and receiving:

  • Where do I ship my sample for Endocrinology testing?
  • Our direct address is: 
    3230 VM3B 
    1089 Veterinary Medicine Drive 
    Davis, CA 95616

    UPS/Fed Ex says your address is not found.
    Occasionally google maps can’t find us. You may substitute One Shields Ave for the street address of 1089 Veterinary Medicine Drive. Shields Ave is a generic UC Davis street address. Please leave 3230 VM3B as the building and room number.
  • Can I ship samples using [insert UC Davis Vet lab] FedEx label?
  • We do not recommend using another lab’s shipping program as the samples will go to that lab instead of to us. This will delay results.  In addition, you may be barred from using the labs’ Fed Ex program. We offer Reduced-Rate FedEx labels, please call the lab for more information.
  • Can I include a sample for another UC Davis Vet lab in the box with my Endo Lab submission?
  • We cannot guarantee quick transfer of your sample to another lab here on campus so it is best to ship your sample to the intended lab. Not all the labs are close to each other on campus, and it may involve a drive for an unlucky lab technician.
  • What should I do with my separated serum if I cannot ship it right away (due to weather, timing, weekend)?
  • We recommend storing separated serum in the freezer (preferably non-frost-free) if you are not able to send it right away. The frozen serum should be good for weeks. Storage in the refrigerator for a day is fine.
  • Can I add a test on after I receive results?
  • We keep serum samples for about three to four weeks after testing. If there is enough serum for the requested test, we are happy to add it on.

Payment and accounts:

  • Can you bill my clinic for testing?
  • Billing can be arranged on a case by case basis. Please contact the lab if payment by credit card is not possible.
  • Do you offer bulk pricing?
  • We only offer bulk pricing on a case by case basis. 
  • Do I need to have an account to send samples to the Endo Lab?
  • No, we take credit cards as our primary form of payment. You do not need to set up an account for us. 
  • Can I pay by check?
  • Yes, only if you include the check with your shipment, and address the check to "UC Regents".

 

References:

[1] Nagashima JB, Hansen BS, Songsasen N, Travis AJ, Place NJ. Anti-Mullerian Hormone in the Domestic Dog during the Anestrus to Oestrous Transition. Reprod Domest Anim. 2016;51:158-64.

[2] Place NJ, Cheraskin JL, Hansen BS. Evaluation of combined assessments of serum anti-Mullerian hormone and progesterone concentrations for the diagnosis of ovarian remnant syndrome in dogs. J Am Vet Med Assoc. 2019;254:1067-72.

[3] Place NJ, Hansen BS, Cheraskin JL, Cudney SE, Flanders JA, Newmark AD, et al. Measurement of serum anti-Mullerian hormone concentration in female dogs and cats before and after ovariohysterectomy. J Vet Diagn Invest. 2011;23:524-7.