AMH, testosterone, estradiol and LH in cats and dogs: is the animal neutered?

What it shows

• AMH (anti-Müllerian hormone) is made only by the ovaries in females and by the testicles in males. It circulates whether or not a female is in heat, so no special timing or hormone injection is needed. Positive means gonadal tissue is present; negative fits a spayed or castrated animal.
• Testosterone is the male hormone made by the testicles. A baseline sample is usually enough in a mature male to tell a castrated animal from one with a retained testicle.
• Testosterone after hCG is a stimulation test: a sample is taken before and two hours after an injection of hCG (or GnRH), a hormone that drives the testicles. The paired values separate fully castrated males from those with a retained testicle or a piece of testicle left behind. It is used when the baseline testosterone is equivocal.
• Estradiol (17-beta) is the main estrogen. It is high during heat in an intact female and can be raised by hormone-producing tumours or by contact with estrogen from outside.
• LH (luteinizing hormone) comes from the pituitary. Ovaries hold it down; after their removal it stays high. The test is qualitative.

Higher than reference — what it may be a sign of

• AMH positive — ovarian or testicular tissue is present: an intact animal, a retained testicle or an ovarian remnant.
• Testosterone high in a male thought to be castrated — a retained testicle or testicular tissue is likely.
• Estradiol high in a spayed female — active ovarian tissue, exposure to an estrogen source such as an owner’s hormone cream (described in a cat), or, if the ovaries are not the source, the adrenal glands. In male dogs, an estrogen-producing testicular tumour (Sertoli cell tumour).
• LH positive — fits an animal without ovaries, but a single high value does not prove it: an intact female during the LH surge before ovulation is positive too.

Lower than reference

• AMH negative — fits a spayed or castrated animal. It does not fully rule out an ovarian remnant, which is why labs pair it with progesterone; an intact female past reproductive age can also be negative.
• Testosterone low — fits a castrated male; testosterone is lower in autumn and winter in cats, which is when stimulation helps.
• LH negative — points to an animal that still has ovaries, or to estrogen from another source suppressing LH.

Look at together with

• Progesterone on the same sample as AMH: the corpus luteum makes progesterone but not AMH, so high progesterone with negative AMH after ovulation can still point to a remnant.
• Vaginal cytology and behaviour — evidence of estrogen during heat-like signs.
• Ultrasound — to look for a retained testicle or ovarian tissue.

Units and conversion

AMH is often reported qualitatively — positive, negative or inconclusive; when a number is given, it is in ng/mL. Testosterone is reported in nmol/L or ng/mL: 1 ng/mL equals 3.467 nmol/L. Estradiol is reported in pmol/L or pg/mL: 1 pg/mL equals 3.671 pmol/L. LH has no unit on the form: the kit reads below 1 ng/mL as negative and above 1 ng/mL as positive. In the app each row keeps what is printed on the form.

Reference range

The reference range is on your lab’s form, and it depends on the reproductive status the clinic writes on the request, so that information matters. One university laboratory expects a castrated dog or cat to have testosterone below 0.7 nmol/L, while males with a retained testicle are typically above 1.0 nmol/L. For AMH, labs ask to wait at least one month after surgery so the hormone can clear from the blood.

Cats and dogs

Sources

1. Cornell University Animal Health Diagnostic Center — Canine Reproductive Function Tests
2. Cornell University Animal Health Diagnostic Center — Feline Reproductive Function Tests
3. Michigan State University Veterinary Diagnostic Laboratory — Endocrinology: Assessment of Reproduction
4. Whitbread T. J. Serologic Test Kits (canine and feline luteinizing hormone: ovulation timing and ovariectomy status). Merck Veterinary Manual, professional version
5. Merck Veterinary Manual — Ovarian Remnant Syndrome in Small Animals (professional version)
6. Merck Veterinary Manual — Endocrinological Paraneoplastic Syndromes in Small Animals (hyperestrogenism)
7. Cornell Riney Canine Health Center — Ovarian remnant syndrome (ORS)
8. Dresner E. O., Norsworthy G. D. Consider This Case: Estrus in a Spayed Cat. Today’s Veterinary Practice, 2013