The hypothalamic-pituitary-adrenal axis plays a central role in maternal physiological adaptations to pregnancy. Wharfe et al. set out to determine if these changes are mediated via the clock rhythm genes in the hypothalamus.

Using a mouse model, they found that expression of all the clock genes in the anterior hypothalamus varied markedly throughout gestation. Maternal corticosterone levels increased significantly (up to 14-fold on day 14 of pregnancy), but this was not accompanied by a similar alteration in plasma adrenocorticotrophin (ACTH) levels, which were 28% lower on day 14 compared with non-pregnant levels. Additionally, the daily circadian release of corticosterone was maintained up to day 14 of gestation, but this rhythm was lost by day 18.

Overall, the data indicate that while changes to the central circadian clock during pregnancy are likely to contribute to maternal physiological adaptations, neither these hypothalamic clock genes nor plasma ACTH levels seem to power the increase in maternal corticosterone after mid-gestation.

Read the full article in Journal of Endocrinology 228 135–147