Hypothyroidism Identified as Growth Suppressing Factor During Severe PRRS Infections

Farmscape for May 5, 2021

Full Interview 11:59 Listen

Scientists with the Western College of Veterinary Medicine are striving to address the reductions in growth performance in pigs associated with severe infections. Hypothyroidism is a condition where the thyroid gland fails to release enough thyroid hormone into the bloodstream, slowing metabolism. Researchers with the Western College of Veterinary Medicine are exploring the effect of disease on thyroid hormone levels in pigs and potential treatment options for the resulting reduction in growth performance. Dr. Glenn Hamonic, a Post Doctoral Fellow working in PRRS research, says during severe infections thyroid hormone levels can drop to 50 percent of normal.

Clip-Dr. Glenn Hamonic-Western College of Veterinary Medicine:
We started looking at it in PRRS and what we found is, in serious PRRS infections, whether it’s in a fetus, a gilt or a nursery pig, when they reach that peak thyrenia they will be hypothyroid. Hypothyroidism isn’t typically something you would associate with infections.
Generally, if something is hypothyroid that means they have an issue with their thyroid gland itself or in the hypothalamic pituitary thyroid access which controls the set point level of thyroid hormone inside the body. But in significant disease, so infections where the pigs are getting really quite sick, there’s actually a suppression of that thyroid hormone and, when the animals reach their peak sickness, their thyroid hormones drop to the lowest they’ll drop to. In the case of PRRS we can see that the thyroid hormones drop to about 50 percent of normal levels. In other diseases that we’ve started looking at such as Porcine circovirus or Mycoplasma hyopneumoniae or Salmonella infection, it won’t be to the same extent as we’ve seen in PRRS but certainly if you look at the animals that aren’t growing and aren’t performing as well, those animals are the ones that are having a transient hypothyroidism. As they get sick, their thyroid hormone levels are starting to drop and those are the animals that aren’t growing and aren’t performing as well.

Dr. Hamonic says the pig’s entire system is dysregulated during these significant infections so the end goal is to find ways to alleviate the growth suppression that happens with these infections.

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