[Thyroxine and triiodothyronine blood plasma concentrations in sows and newborn pigs]

Plasma thyroxine (T4) and triiodothyronine (T3) concentrations of 11 sows and their 56 fetuses have been measured by radioimmunoassay between 80--112 days of intrauterine development. Similar measurements were carried out in 20 piglets of 2 litters up to 24 hours of age and in sows; the latter within a period of 3 days before and 3 days after parturition. The average T3 concentration in the fetus was 0.30--0.41 ng/ml, that of T4 showed great variations between the litters. After 106 and 112 days of intrauterine development either a high (84 +/- and 159 +/- 24 ng/ml) or a low T4 concentration (18 +/- 10 and 11 +/- 5ng/ml) has been confirmed. At birth sows had a significantly lower plasma hormone concentration than the newborn piglets. After parturition the T4 concentration than the newborn piglets. After parturition the T4 concentration decreased significantly in the first 12 hours of life, while that of T3 increased significantly. In sows, pre- and intrapartal serum T4 and T3 concentrations were significantly lower than post partum.