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Equine Cushing's Disease: Part II
- By Fred Nostrant, DVM
- •
- 26 Apr, 2024
The TRH Stimulation Test
Here's how the equine TRH stimulation test works:
1. Preparation: Before conducting the test, the horse is typically fasted from grain for a period of time to ensure accurate blood sampling and minimize the influence of recent feed intake on hormone levels. Access to hay and forage is allowed.
2. Administration of TRH: TRH, or thyrotropin-releasing hormone, is a hormone produced by the hypothalamus, a region of the brain that regulates various physiological processes, including hormone secretion by the pituitary gland. In the TRH stimulation test, a veterinarian administers a specific dose of synthetic TRH intravenously or intramuscularly to the horse.
3. Blood Sampling: Just prior to and following the administration of TRH, blood samples are collected from the horse at specific time intervals, typically at baseline (before TRH administration) and at designated time points after TRH administration, such as 10, 20, and 30 minutes.
4. Measurement of Hormone Levels: The blood samples collected during the test are analyzed to measure the concentration ACTH. ACTH is the hormone primarily associated with PPID, and its levels are often elevated in affected horses due to dysfunction of the pituitary gland.
5. Interpretation of Results: The equine TRH stimulation test helps veterinarians assess the pituitary gland's response to TRH stimulation. In horses with PPID, the pituitary gland may exhibit an exaggerated or prolonged release of ACTH in response to TRH administration compared to healthy horses. Elevated ACTH levels following TRH stimulation are indicative of pituitary dysfunction and support a diagnosis of PPID.
It's important to note that the equine TRH stimulation test is just one of several diagnostic tools used to evaluate horses suspected of having PPID. Veterinarians may also consider clinical signs, such as abnormal hair growth, excessive drinking and urination, lethargy, and laminitis when making a diagnosis of PPID and determining the appropriate treatment and management plan for affected horses.
Overall, the equine TRH stimulation test plays a valuable role in diagnosing PPID and guiding treatment decisions, helping veterinarians provide optimal care for horses affected by this common endocrine disorder. This test allows us to catch horse's in the early stages of Equine Cushing's Disease so that we can prevent the significant health problems caused by this disease.
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Pasture Management for Springtime Grass
After months of barren ground or snow covered fields, we are slowly starting to see the gorgeous signs of spring in New England once again. The horses are shedding and eagerly awaiting any chance they have to nibble some delicious green grass. Below we provide very helpful guidelines for the slow controlled introduction to keep our horses safe and healthy.
Horses that always live outside have the benefit of mother nature's slow introduction to grass as it grows through the first weeks of spring. Horses living in stalls with only partial day turnout have to be more strictly controlled in their introduction to pasture to prevent the serious trouble that can occur with too much fresh grass too quickly. Over indulgence in grass can result in gas colic and laminitis. So what can you do to protect your horse from the potential hazards of too much grass too quickly?
Here are guidelines to assist you in coming up with a pasture introduction plan:
Horses on 2-12 hours a day of pasture:
If you have limited pasture but still want your horse to reap the benefits of daily turnout you probably fall into this category. Most horses in a boarding situation with access to grass will be in this group. Take care to closely follow a pre-determined time scale of introduction for these horses. We recommend the following graduated schedule:
Days 1-3: 20 min/day
Days 4-6: 1hr/day
Days 6-9: 2 hrs/day
Days 10-12: 3 hrs/day
Day 13 and beyond: unlimited in horses who are not overweight or sensitive.
You can also use a grazing muzzle (see below) if you need to introduce pasture more rapidly. With a grazing muzzle you can add 20 min per day of turnout until on full turnout. Once on full turn out keep muzzle on for about a week then alternate every other day for a week then it should be safe to remove the grazing muzzle.
