The impact of maternal synthetic glucocorticoid administration in late pregnancy on fetal and early neonatal hypothalamic-pituitary-adrenal axes regulatory genes is dependent upon dose and gestational age at exposure.

In this study, we determined the gene and/or protein expression of hypothalamic-pituitary-adrenal (HPA) axis regulatory molecules following synthetic glucocorticoid exposures. Pregnant sheep received intramuscular saline or betamethasone (BET) injections at 104 (BET-1), 104 and 111(BET-2) or 104, 111 and 118 (BET-3) days of gestation (dG). Samples were collected at numerous time-points between 75 dG and 12 weeks postnatal age. In the BET-3 treatment group, fetal plasma cortisol levels were lower at 145 dG than controls and gestational length was lengthened significantly. The cortisol:adrenocorticotropic hormone (ACTH) ratio in fetal plasma of control and BET-3 fetuses rose significantly between132 and 145 dG, and remained elevated in lambs at 6 and 12 weeks of age; this rise was truncated at day 145 in fetuses of BET-3 treated mothers. After BET treatment, fetal and postnatal pituitary proopiomelanocortin mRNA levels were reduced from 109 dG to 12 weeks postnatal age; pituitary prohormone convertase 1 and 2 mRNA levels were reduced at 145 dG and postnatally; hypothalamic arginine vasopressin mRNA levels were lowered at all time-points, but corticotrophin-releasing hormone mRNA levels were reduced only in postnatal lambs. Maternal BET increased late fetal and/or postnatal adrenal mRNA levels of ACTH receptor and 3ß hydroxysteroid dehydrogenase but decreased steroidogenic acute regulatory protein and P450 17-α hydroxylase. The altered mRNA levels of key HPA axis regulatory proteins after maternal BET injections suggests processes that may subserve long-term changes in HPA activity in later life after prenatal exposure to synthetic glucocorticoids.