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Rapeseed-enriched diet and low-level thiouracil administration in cattle : impact on thyroid hormone metabolism

Author
Organization
Project
THYREOMERK RF 12/6260
Abstract
The thyroid hormone metabolism is of major importance in maintaining a body’s homeostasis. This hormonal pathway may become severely disturbed by several pharmaceuticals of which one group, the thyreostats, has been purposely designed for, in order to treat hyperthyroidism. Unfortunately, the same drug became popular as fattening substance in live stock industry, threatening the animals’ health in the first place by influencing the thyroid hormone metabolism, but also compromising the costumers’ health because of carcinogenic and teratogenic residues. Despite the current ban on the (ab)use of thyreostats for weight-gain purposes, low level occurrence of urinary thiouracil is currently raising questions on possible low-level abuse. The recently demonstrated endogenous origin of thiouracil might be another explanation. In this study we subjected 7 cows and 7 calves to either a low-dose synthetic thiouracil treatment (0.20 g/100 kg per os; daily in the morning) or a rapeseed-enriched (30%) diet (ad libitum), with the purpose to monitor the systemic levels of thyroxine (T4), tri-iodothyronine (T3) and reverse-triiodothyronine, as a reflection of (possible) disturbance of (thyroid hormone related) homeostasis. An acclimatization period was followed by a one- (thiouracil administration) to three- (rapeseed enriched diet) week treatment period. In case of synthetic thiouracil treatment, a one-week washout period was included as well. Thyroid hormone analyses were performed by UHPLC-MS/MS in bovine serum sampled three times a day. Basal thyroid hormone levels were significantly (but differently) influenced in both calves and cows. In general, the calves metabolism was promptly reacting with a shift-to-above from baseline levels for T3 and T4 after onset of both treatments, while for cows major impact was seen following synthetic thiouracil treatment resulting in disturbance of the circadian rhythm characterized by a sudden decrease of T3, and parallel increase of rT3, at night. These increased rT3 values were also observed after a rapeseseed enriched diet, without decrease of T3.
Keywords
Thiouracil, Thyroid, cattle, Rapeseed

Citation

Please use this url to cite or link to this publication:

Chicago
Wauters, Jella, Julie Kiebooms, Julie Vanden Bussche, Eric Fichant, Philippe Delahaut, Lieven Van Meulebroek, and Lynn Vanhaecke. 2016. “Rapeseed-enriched Diet and Low-level Thiouracil Administration in Cattle : Impact on Thyroid Hormone Metabolism.” In EuroResidue VIII, Posters.
APA
Wauters, Jella, Kiebooms, J., Vanden Bussche, J., Fichant, E., Delahaut, P., Van Meulebroek, L., & Vanhaecke, L. (2016). Rapeseed-enriched diet and low-level thiouracil administration in cattle : impact on thyroid hormone metabolism. EuroResidue VIII, Posters. Presented at the EuroResidue VIII : conference on residues of veterinary drugs in food.
Vancouver
1.
Wauters J, Kiebooms J, Vanden Bussche J, Fichant E, Delahaut P, Van Meulebroek L, et al. Rapeseed-enriched diet and low-level thiouracil administration in cattle : impact on thyroid hormone metabolism. EuroResidue VIII, Posters. 2016.
MLA
Wauters, Jella, Julie Kiebooms, Julie Vanden Bussche, et al. “Rapeseed-enriched Diet and Low-level Thiouracil Administration in Cattle : Impact on Thyroid Hormone Metabolism.” EuroResidue VIII, Posters. 2016. Print.
@inproceedings{8028001,
  abstract     = {The thyroid hormone metabolism is of major importance in maintaining a body{\textquoteright}s homeostasis. This hormonal pathway may become severely disturbed by several pharmaceuticals of which one group, the thyreostats, has been purposely designed for, in order to treat hyperthyroidism. Unfortunately, the same drug became popular as fattening substance in live stock industry, threatening the animals{\textquoteright} health in the first place by influencing the thyroid hormone metabolism, but also compromising the costumers{\textquoteright} health because of carcinogenic and teratogenic residues. Despite the current ban on the (ab)use of thyreostats for weight-gain purposes, low level occurrence of urinary thiouracil is currently raising questions on possible low-level abuse. The recently demonstrated endogenous origin of thiouracil might be another explanation. In this study we subjected 7 cows and 7 calves to either a low-dose synthetic thiouracil treatment (0.20 g/100 kg per os; daily in the morning) or a rapeseed-enriched (30\%) diet (ad libitum), with the purpose to monitor the systemic levels of thyroxine (T4), tri-iodothyronine (T3) and reverse-triiodothyronine, as a reflection of (possible) disturbance of (thyroid hormone related) homeostasis. An acclimatization period was followed by a one- (thiouracil administration) to three- (rapeseed enriched diet) week treatment period. In case of synthetic thiouracil treatment, a one-week washout period was included as well.  Thyroid hormone analyses were performed by UHPLC-MS/MS in bovine serum sampled three times a day. 
Basal thyroid hormone levels were significantly (but differently) influenced in both calves and cows. In general, the calves metabolism was promptly reacting with a shift-to-above from baseline levels for T3 and T4 after onset of both treatments, while for cows major impact was seen following synthetic thiouracil treatment resulting in disturbance of the circadian rhythm characterized by a sudden decrease of T3, and parallel increase of rT3, at night. These increased rT3 values were also observed after a rapeseseed enriched diet, without decrease of T3.},
  author       = {Wauters, Jella and Kiebooms, Julie and Vanden Bussche, Julie and Fichant, Eric and Delahaut, Philippe and Van Meulebroek, Lieven and Vanhaecke, Lynn},
  booktitle    = {EuroResidue VIII, Posters},
  language     = {eng},
  location     = {Egmond aan Zee, The Netherlands},
  title        = {Rapeseed-enriched diet and low-level thiouracil administration in cattle : impact on thyroid hormone metabolism},
  url          = {http://www.euroresidue.eu/images/posters2016/Poster\%20047.pdf},
  year         = {2016},
}