Weaning stress induced alterations to the hypothalamic-pituitary-thyroid and -adrenal axes in swine

Combined modulation of the hypothalamic–pituitary–thyroid (HPT) and hypothalamic–pituitary–adrenal (HPA) axes is known to play a critical role in maintaining physiological stability in response to stress. In this study, stress induced modulation of these axes was examined using 20 pigs/treatment either weaned (WN), weaned with feed/water restriction 9 h (FR), transported 9 h (TRANS), or remaining with sow (SOS) and euthanized at 32 or 56 h post-weaning. Serum cortisol, thyroxine (T4), and triiodothyronine (T3) were measured before weaning and after 24, 32, and 56 h with no difference in cortisol concentrations among treatments at any timepoint. However, both T3 and T4 decreased post-weaning in FR, TRANS, and WN compared to SOS. Expression of 23 genes of interest was evaluated across the hypothalamus, pituitary, thyroid, and adrenal glands of TRANS and SOS pigs at 56 h to understand the underlying mechanism. TSHB, DIO3, and POMC expression was decreased in the pituitary while DIO3 in the thyroid was increased, with upregulation in MC2R also observed. Collectively, these results suggest acute stressors in swine can induce type I allostasis within the HPT axis and modulate sensitivity within the HPA.