Hair cortisol levels as a retrospective marker of hypothalamic-pituitary axis activity throughout pregnancy: comparison to salivary cortisol

Abstract

Maternal stress during pregnancy is associated with negative maternal/child outcomes. One potential biomarker of the maternal stress response is cortisol, a product of activity of the hypothalamic-pituitary-adrenal axis. This study evaluated cortisol levels in hair throughout pregnancy as a marker of total cortisol release. Cortisol levels in hair have been shown to be easily quantifiable and may be representative of total cortisol release more than single saliva or serum measures. Hair cortisol provides a simple way to monitor total cortisol release over an extended period of time. Hair cortisol levels were determined from each trimester (15, 26 and 36 weeks gestation) and 3 months postpartum. Hair cortisol levels were compared to diurnal salivary cortisol collected over 3 days (3 times/day) at 14, 18, 23, 29, and 34 weeks gestational age and 6 weeks postpartum from 21 pregnant women. Both salivary and hair cortisol levels rose during pregnancy as expected. Hair cortisol and diurnal salivary cortisol area under the curve with respect to ground (AUCg) were also correlated throughout pregnancy. Levels of cortisol in hair are a valid and useful tool to measure long-term cortisol activity. Hair cortisol avoids methodological problems associated with collection other cortisol measures such as plasma, urine, or saliva and is a reliable metric of HPA activity throughout pregnancy reflecting total cortisol release over an extended period.

Figure 1

Hair and salivary AUCg cortisol increase during pregnancy. A) RM One Way ANOVAs revealed that first trimester salivary AUCg cortisol levels were lower in the first trimester relative to the second (p=0.02) and third trimesters (p<0.001). In addition, the postpartum period AUCg levels were lower than the first (p=0.02), second (p<0.001) and third trimesters (p<0.001). No other differences were detected. B) Third trimester hair cortisol levels are significantly elevated relative to first trimester (<0.001; One Way RM ANOVA) and postpartum levels (0.004; One Way RM ANOVA). No other differences were detected. Bars represent means ± SEM. * p<0.05, *** p<0.001

Figure 2

Salivary and hair cortisol levels during pregnancy (ug/dl). A) Mean salivary cortisol levels at each collection time point by trimester during the perinatal period reflecting the expected diurnal curve across the day. Two Way RM ANOVA demonstrated a significant trimester x time interaction (p=0.007), such that there were differences in the wake+30 min collection time point between first and second trimester (p<0.001), first and third trimester (p=0.001), second trimester and postpartum period (p<0.001) and the third trimester and postpartum period (p<0.001). In addition, salivary cortisol levels at wake+30 min significantly differed from both lunch and wake+10 hour time points at every trimester. No other differences were detected. Error bars represent ± SEM. B) Individual salivary cortisol levels at waking +30 min sample across pregnancy and the postpartum period. The line connects the respective means of salivary cortisol at each stage of pregnancy. This figure indicates the expected increase during pregnancy as well as the variability across mothers during pregnancy that we have noted elsewhere [22].