Steroid axis in pregnancy

1) Serum cortisol levels increase 2-3 fold by term. 

There is an oestrogen-induced increase in production of cortisol binding globulin. 

 Free serum cortisol and urinary free cortisol are however also increased in pregnancy

2) ACTH levels are lower in pregnancy compared to non-pregnant but increase with increasing gestation

3) The placenta produces both ACTH and CRH - the relationship between these placental hormones and maternal adrenal function is unknown.