The relationship of nocturnal melatonin to estradiol and progesterone in depressed and healthy pregnant women

Purpose: To assess the relationship between nocturnal plasma melatonin and serum estradiol (E₂) and progesterone (P₄) levels in depressed pregnant women (DW) and matched healthy women (HW). Methods: We used analysis of variance (ANOVA) and linear regression analyses on data obtained from pregnant HW and DW. Results: Log E₂ and log P₄ were positively correlated with measures of melatonin quantity in HW (p<0.05) but not DW, controlling for age. Log E₂ and log P₄ were positively correlated with melatonin offset and duration in DW (p<0.01) but not HW. Conclusions: Pregnant DW may be less sensitive than HW to modulation of melatonin secretion by E₂ and P₄. That melatonin timing measures are more sensitive to E₂ and P₄ variation in DW may reflect a circadian system more attuned to the need for realignment in DW than in HW. These altered sensitivities to reproductive hormones may reflect a biologic vulnerability that predisposes some pregnant women to depression.