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  Discussion on Elevated progesterone and behavior problems with mare.
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Posted on Monday, Aug 14, 2000 - 2:38 am:

My 5 yr old mare went back to the trainer, she'd occasionally act up, then started rearing at the trainers. She was doing this only when in season, and that's lasted too long and too often. The vet did ultrasound, then checked progesterone near the end of her last heat cycle. Via this lab, normal is 1 or less, her level was 9.1, which I was told would likely cause behavior problems. Last cycle, the trainer was on her, and she reared, went forward on her hind legs, and tried to mount another mare. Her behavior to other horses is more stallion like as well.
I an looking for some answers and potential solutions. If she's breed able, I'm told this may help, or meds, or removing her female parts (making her whatever we call a female gelding). She's superbly bred, and got it all. I've raised her from a yearling, love this horse, allot of effort, and I'd like to keep and ride her (provided we straighten this problem out.
Any good information is welcome. Thanks, Dusty

Posted on Monday, Aug 14, 2000 - 9:18 am:

If the progesterone level is really 10Xs normal FOR THAT STAGE of THE CYCLE, then a granulosa cell tumor is very likely the cause of your trouble see: The Horseman's Advisor: Training Horses: Behavioral Problems: Granulosa Cell Tumors.
DrO

Posted on Tuesday, Aug 15, 2000 - 2:15 am:

Thank you. I did read your article on Granulosa Cell Tumor. The level of progesterone was 9.1 with normal being 1 or less (per the local vet). Ultrasound of the ovaries indicated nothing abnormal, and was sent to U of IL, who also found nothing abnormal. The vet suggested two injections (a day apart) to bring her back into her cycle, however, she came back in (strong) on Saturday. She has reared several times, and is very skiddish during her cycle, calm and nice otherwise. Last time she reared and tried to mount the mare in front of her who was very in cycle. Her aggression to other horses at this time is stallion like vs mare like.
All that said, having read the article you suggested, I'm not clear as to a step by step where we need to go next to figure this out. I would appreciate some specific suggestions and/or a paid telephone consult, perhaps with the local vet.

Posted on Tuesday, Aug 15, 2000 - 3:37 pm:

A normal appearence to the ovaries does not rule out GCT (reference: Hinrichs K, Cochran SL, Schelling SH, Steckel RR. Related Articles Granulosa-theca cell tumor associated with an ovulation fossa and normal ovarian stroma in a mare. J Am Vet Med Assoc. 1992 Mar 1;200(5):696-8.) however it is unusual.

I cannot think of any other way to account for the ultrahigh progesterone however. Neither can I think of a way to further diagnose the problem other than remove the ovary, but which one? I would take the larger of the two (measure them several times and average) and keep my fingers crossed. If that does not reduce the hormone levels I would remove the other and figure I didn't want to breed her anyway.
DrO
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