Serum hormones in the perinatal pig and the effect of exogenous insulin on blood sugars.

Growth hormone (GH), insulin, cortisol, triiodothyronine (T3) and thyroxine (T4) were determined in serum of fetal pigs at 90, 100, 110 and 114 days of gestation and of newborn pigs at 1 and 24 hours of age. Fetal GH, T3 and cortisol increased between 90 and 110 days. GH concentration decreased between 110 and 114 days, while T3 and cortisol were unchanged. T4 was variable in fetal pigs and no relationship with T3 levels was apparent. Fetal insulin was constant at approximately 10 muU/ml. In newborn pigs there was a 3-fold and 2-fold increase in T3 and T4, respectively, during the first 24 hours of life. Cortisol in serum more than doubled during the first hour. Between 1 and 24 hours, there was a simultaneous decrease in cortisol and a 6-fold increase in insulin. No significant change in GH was noted during this time. Intraperitoneal insulin injected one hour before sacrifice induced a hypoglycemic response in newborn pigs, but not in fetal pigs.