Effect of somatostatin and thyrotrophin-releasing hormone on the levels of growth hormone in the circulation of the chronically catheterized pig fetus in utero.

The effects of i.v. administration of thyrotrophin-releasing hormone (TRH) and of somatostatin on circulating plasma levels of porcine GH in the chronically catheterized pig fetus have been examined. Growth hormone levels increased markedly (P less than 0.01) following TRH administration, but there was no change in thyroxine levels by 1 h after treatment. Administration of somatostatin caused a significant (P less than 0.05) decrease in mean GH levels, but the response was variable between pigs. Saline administration had no significant effect on GH levels. These results suggest that the mechanisms regulating postnatal GH release are present in the fetal pig, but may not be fully developed 8-12 days before delivery.