Measuring corticotropin-releasing hormone in pregnant women - comparing blood collection protocols for epidemiological studies

Stress questionnaires and stress biomarkers during pregnancy

OBJECTIVE

Both self-reported indicators of stress and hormones such as cortisol and corticotrophin-releasing hormone (CRH) have been examined in relation to preterm birth. Although these hormones have been interpreted as biomarkers of stress, it is unclear whether psychosocial measures are empirically associated with biomarkers of stress in pregnant women.

METHODS

We analyzed data from 1,587 North Carolina pregnant women enrolled in the Pregnancy, Infection,and Nutrition study during 2000-2004 who provided at least one saliva sample for cortisol measurement or blood samples for CRH at 14-19 and 24-29 weeks' gestation. Cortisol measures were limited to those taken between 8 and 10 a.m. Perceived stress, state-trait anxiety, coping style, life events, social support, and pregnancy-specific anxiety were measured by questionnaires and interviews. Spearman correlations and multiple regressions were used to describe the relationship among the measures of stress.

RESULTS

No correlations larger than r = 0.15 were seen between reported psychosocial measures and cortisol or CRH. Women with demographic characteristics associated with poor pregnancy outcomes (unmarried, African-American, young, low pre-pregnancy body mass index) reported higher levels of stress but did not consistently have higher levels of stress hormones. Pre-eclampsia was associated with higher CRH, but not with higher cortisol.

CONCLUSIONS

The relationship between measurements of reported stress and biomarkers is not straightforward in large epidemiological studies of pregnancy.

Preparation, piloting and validation for a longitudinal birth cohort study

No longitudinal study should go into the field prior to detailed piloting and validation studies of the measures and techniques to be used. Preparation should also involve the training of staff, the acquisition of space and appropriate equipment, and liaison with the community and ethical committees as well as with scientific collaborators. Because different measures will continually be introduced as the participants age, the preparation, piloting and validation studies have to be ongoing. Here we describe some of the different strategies that should be used.

Maternal levels of corticotropin-releasing hormone during pregnancy in relation to adiponectin and leptin in early childhood

BACKGROUND

Fetal glucocorticoid exposure is associated with later development of features of the metabolic syndrome such as central obesity and insulin resistance. Fat tissue, especially visceral fat, produces adiponectin, which is inversely associated with insulin resistance in older children and adults. Adipocytes also produce leptin, directly related to measures of adiposity. It is unknown how the secretion of these hormones in early childhood is related to pregnancy levels of CRH, a proxy of fetal glucocorticoid exposure.

AIM

Our aim was to study the relationship of maternal midpregnancy CRH levels with offspring levels of adiponectin and leptin in early childhood.

METHODS

The study population consisted of 349 mother-children pairs from Project Viva, a prospective prebirth cohort study from eastern Massachusetts. We created a general linear model with log CRH levels in midpregnancy maternal blood as the predictor and adiponectin and leptin measured in the 3-yr-old offspring as outcomes, adjusting for covariates.

RESULTS

The means (sd) of log CRH, adiponectin, and leptin were 4.97 (0.65) log pg/ml, 22.4 (5.8) microg/ml, and 1.9 (1.8) ng/ml. For each unit increment in log CRH, mean value of offspring adiponectin was 1.10 microg/ml (95% confidence interval = 0.06-2.14) higher. We found no association with leptin (-0.08 ng/ml; 95% confidence interval = -0.40-0.24).

CONCLUSIONS

Higher maternal blood levels of CRH were associated with higher levels of adiponectin but unchanged levels of leptin at age 3 yr. The increased adiponectin levels might represent secretion from organs other than fat or reflect a compensatory mechanism to increase insulin sensitivity.

Bioassay research methodology: measuring CRH in pregnancy

BACKGROUND

There are documented associations between elevated maternal corticotropin-releasing hormone (CRH) levels and adverse pregnancy outcomes. However, reports of these findings often lack sufficient detail and rationale regarding the bioassay methodology. This shortcoming can be problematic for researchers who do not possess in-depth laboratory sciences knowledge but who want to include bioassays in their investigations or to evaluate published reports. The quality and reliability of CRH measurement results can be significantly affected by variables encountered during sample collection, processing, storage, and bioassay. Thus, it is important to establish research laboratory protocols that are based on well-informed rationales and to carefully consider and control for relevant variables.

APPROACH

A synthesis of laboratory sciences literature regarding variables affecting CRH measurement in pregnancy is presented. Additionally, consultation with experienced researchers provided an in-depth understanding of CRH measurement. From these sources, a laboratory protocol for clinical research was developed.

RESULTS

Multiple variables that are specific to the reliability of CRH measurement in pregnancy have been identified. These include sample collection methods, sample processing, sample integrity, sample storage, and the actual assay selected.

CONCLUSION

The reliability of CRH measurements can be significantly improved by identifying and controlling for variables encountered during sample collection, processing, storage, and bioassay. Adequate methodological details are difficult to glean solely from the published literature, thus consultation with well-informed researchers is necessary. A protocol for CRH bioassay in clinical research is proposed.

Elevated midpregnancy corticotropin-releasing hormone is associated with prenatal, but not postpartum, maternal depression

CONTEXT

Elevated hypothalamic CRH has been implicated in melancholic major depression in nonpregnant individuals, but the role of placental CRH in maternal prenatal and postpartum depression is largely unexplored.

OBJECTIVE

The objective of the study was to examine the association of maternal midpregnancy plasma CRH levels with prenatal and postpartum depression.

PARTICIPANTS

The study included 800 participants in Project Viva, a pregnancy and childhood cohort.

METHODS

CRH levels were analyzed from blood samples obtained at mean 27.9 wk gestation (+/- 1.3 sd; range 24.6-37.4 wk) and were normalized on the logarithmic scale. Depression was assessed with the Edinburgh Postpartum Depression Scale (range 0-30 points) in midpregnancy and at 6 months postpartum. We used logistic regression to estimate the odds of scoring 13 or more points on the Edinburgh Postpartum Depression Scale as indicative of major or minor depression.

RESULTS

Seventy (8.8%) and 46 (7.5%) women had prenatal and postpartum depression symptoms, respectively. Mean log CRH was 4.93 (+/- 0.62 sd). After adjusting for confounders, an sd increase in log CRH was associated with nearly 50% higher odds of prenatal depression symptoms (odds ratio 1.48, 95% confidence interval 1.14-1.93). Higher CRH levels during pregnancy were unassociated with greater risk of postpartum depressive symptoms. In fact, there was a suggestion that prenatal CRH levels might be inversely associated with risk of postpartum depressive symptoms (odds ratio 0.82, 95% confidence interval 0.58-1.15).

CONCLUSIONS

Elevated placental CRH levels in midpregnancy are positively associated with risk of prenatal depression symptoms but not postpartum depression symptoms.

Maternal corticotropin-releasing hormone levels during pregnancy and offspring adiposity

OBJECTIVE

Animal models suggest that fetal exposure to glucocorticoids can program adiposity, especially central adiposity, later in life. We examined associations of maternal corticotropin-releasing hormone (CRH) levels in the late 2nd trimester of pregnancy, a marker of fetal glucocorticoid exposure, with child adiposity at age 3 years.

RESEARCH METHODS AND PROCEDURES

We analyzed data from 199 participants in Project Viva, a prospective cohort study of pregnant women and their children, At age 3 years, the main outcomes were age-sex-specific BMI z score and the sum of subscapular (SS) and triceps (TR) skinfold thicknesses to represent overall adiposity, and ratio of SS to TR (SS:TR) to represent central adiposity.

RESULTS

Mean (standard deviation) maternal 2nd trimester log CRH was 4.94 (0.56) pg/mL. At age 3, mean (standard deviation) for BMI z score was 0.52 (1.02); for SS + TR, 16.51 (3.94) mm; and for SS:TR, 0.67 (0.17). Log CRH was mildly inversely correlated with birth weight (r = -0.08), chiefly because of its association with length of gestation (r = -0.21) rather than fetal growth (r = -0.004). After adjustment for sociodemographic factors, maternal smoking, BMI, and gestational weight gain, fetal growth, length of gestation, breastfeeding duration, and (for SS:TR only) child's 3-year BMI, each increment of 1 unit of log CRH was associated with a reduction in BMI z score [-0.43; 95% confidence interval (CI), -0.73, -0.14; p = 0.004] and possible reduction in SS + TR (-1.10; 95% CI, -2.33, 0.14; p = 0.08). In contrast, log CRH was associated with higher SS:TR (0.07; 95% CI, 0.02, 0.13; p = 0.007).

DISCUSSION

Fetal exposure to glucocorticoids, although associated with an overall decrease in body size, may cause an increase in central adiposity.