THE EFFECT OF DIETARY FATS ON PLASMA-CONCENTRATIONS OF THYROID-HORMONES IN THE PIG

The intention of the present study was to investigate the effect of di etary fats on plasma concentrations of thyroid hormones. Therefore, ni ne non-gravid female pigs were fed a ration based on the energy requir ement for maintenance and the test fat (beef tallow, olive oil or soyb ean oil) in amounts of 250 g per day during a period of two weeks. Acc ording to a cross-over design, each animal received each fat once. Bet ween the two experimental periods all the animals were fed the basal r ations without addition of far for three weeks, Blood samples were dra wn at the end of each experimental period after the pigs were fasted f or 12h and the concentrations of thyroxine and tri-iodothyronine in pl asma were determined. The concentrations of total and free thyroxine i n plasma were nor, influenced by the type of fat. In contrast, there w as an effect, dependent upon the type of fat, on the concentration of triiodothyronine in plasma. The tri-iodothyronine concentrations were lower after feeding beef tallow than after feeding soybean oil or oliv e oil; soybean oil and olive oil caused similar concentrations of tri- iodothyronine. In conclusion, the results of the study indicate that t he type of fat influences the metabolism of thyroid hormones.