skinny neck etc.= hypothyroid?

[la ponita]

I posted a while back re: a 9-10 hh pony I recently bought as a companion. She's 10, had a foal this past year, and was on a conscientious nutrition program; the basic conclusion was likely 'bit conformation/bit [lack of] conditioning/muscling up'.

Last week I had my vet out to check a few things, and his intial reaction upon examining her was "looks like pony might be hypothyroid...keep an eye on her weight, and do what you can with exercise". He indicated that verificiation of the condition would of course involve bloodwork.

This pony is peppy and happy from all I can see...I'm just wondering if anyone has or has had a horse/pony with any similarities etc.??

[old_woman]

Hi there.

First of all I need to check whether the vet said hypo- or hyperthyroid. Hyperthyroidism is rare in adult horses, so I will assume it is hypothyroidism. You would be surprised how many people get the two prefixes confused!

In simple terms, the prefix "hypo" means less, low or insufficient, and the prefix "hyper" means more, high, or too much.
Thus, hypothyroid indicates a state in which the thyroid gland, for whatever reason (there are several), is UNDERactive, producing insufficient thyroid hormone/s; and hyperthyroid indicates a state in which the thyroid gland is OVERactive and there is an overproduction of one or more of the thyroid hormones or precursors.

A blood sample to measure the two thyroid hormones, T3 and T4, is often taken to confirm a suspected diagnosis of hypo OR hyperthyroid, but there is a major problem in that the blood levels of these hormones are highly variable in the healthy horse, both long term and throughout each day, and do not accurately reflect thyroid function. In any case, there are so many mechanisms at work in the production of thyroid hormones that what might seem like a simple answer of supplementing them artificially if levels are low, is not simple at all and may profoundly affect other systems of the horse in unexpected and/or unwanted ways. And of course, it is often a problem in ANOTHER part of the endocrine system that results in the incorrect level of thyroid activity overall.

As a long-time nurse in endocrinology before I retired, this is one of the better articles I have read on hypothyroid conditions in the horse, albeit that it is fairly old. It spells out some of the problems involved in finding a correct diagnosis and treatment for hormonal problems, given the complex interactions in the endocrine system:
http://www.horses-and-horse-information.com/articles/0496hypo.shtml

I think your vet is on the right track by suggesting that you get everything else sorted out as best you can before going down the bloodwork route, which can be lengthy and may still not result in any firm conclusion or final diagnosis.

Good luck!

[la ponita]

Thanks for all the info, 'O.W.' ! Checked out the link also, so now I feel semi-conversant on the issue...and yes, the mare is hyPO; I have a few relatives who have been hyPER or hyPO, so I have that one straight! Thanks again :) .