Endocrine Function in an Anencephalic Infant

TLDR

The study measured ACTH, GH, insulin, TSH, T4, T3, and cortisol in cord blood and serial plasma samples of a full‑term anencephalic infant, and administered TRF, LVP, ACTH, and TSH to assess endocrine responsiveness. TSH and ACTH were low until stimulated by TRF and LVP, after which they rose sharply, yet T4, T3, and cortisol remained unchanged; insulin spiked with a glucose drop, indicating the pituitary could release TSH/ACTH but target organs were functionally atrophic, while growth hormone secretion appeared intact.

Abstract

The endocrine function in a fullterm 2.1 kg female anencephalic infant was studied by measuring immunoreactive ACTH, growth hormone, insulin, TSH, T4, and T3 concentrations in umbilical cord blood and serial venous plasma samples obtained at 10–30-min intervals until death. In addition, plasma cortisol and T4 concentrations were determined by competitive protein binding. The following materials were given: TRF (100 mg, iv) at 86 mins; lysinevasopressin (LVP) (2.5U, iv) at 125 mins; α1-24 ACTH (1 mg, im) at 160 min; and TSH (5U, im) at 221 min. Plasma TSH and ACTH concentrations were low in the infant until stimulation by TRF and LVP, respectively. Plasma TSH and ACTH concentrations then increased significantly. There were no corresponding changes in plasma T4, T3, or cortisol concentrations following the elevation in plasma TSH and ACTH concentration. A spike in plasma insulin concentration occurred following injection of vasopressin with a subsequent fall in the plasma glucose concentration. These data indicate that the adenohypophysis of this anencephalic infant contained a readily dischargeable pool of TSH and ACTH. Endogenous secretion or exogenous administration of these tropic hormones did not result in the expected secretory response by their respective target plans presumably due to functional atrophy of the latter. Growth hormone was presumably secreted in significant quantities despite absence of the hypothalamus.