Effect of prolonged intermittent thyrotropin-releasing hormone administration to fetal and neonatal rats

Abstract

Fetal and neonatal rats received daily subcutaneous injections of 10 μg thyrotropin-releasing hormone (TRH) until 7 or 14 days postnatally. At 70 days the pups were challenged with 1 μg TRH intravenously via an indwelling jugular cannula. Basal serum thyroxine, triiodothyronine, and thyroid-stimulating hormone (TSH) concentrations did not differ among the three groups. The mean TSH responses as determined by the mean peak TSH concentration and the total TSH response as determined by planimetry were not significantly different, and there was no significant difference in pituitary TSH content following the TRH challenge among the three groups. This study suggests that the integrity of the hypothalamo–pituitary axis in adult rats cannot be affected by the repeated administration of pharmacologic doses of TRH during the perinatal period.