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The 24‐hour rhythm of oxytocin and Β‐endorphin secretion in human pregnancy
Author(s) -
Lindow S. W.,
Newham A.,
Hendricks M. S.,
Thompson J. W.,
Van Der Spuy Z. M.
Publication year - 1996
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1046/j.1365-2265.1996.8290840.x
Subject(s) - oxytocin , endocrinology , medicine , gestation , pregnancy , circadian rhythm , beta endorphin , endogenous opioid , rhythm , biology , opioid , receptor , genetics
OBJECTIVE Animal work suggests that maternal oxytocin secretion is influenced by the secretion of endogenous opioids in pregnancy. Spontaneous labour and pre‐labour uterine activity follow a 24‐hour rhythm the origin of which has not been explained but may be related to diurnal changes in oxytocin secretion. This study was performed to document the changes over a 24‐hour period in maternal oxytocin and Β‐endorphin secretion.DESIGN A 4‐hourly blood profile was undertaken for a 24‐hour period.PATIENTS Sixteen women with singleton pregnancies of more than 36 weeks gestation and 10 women with pregnancies in the mid trimester were studied.MEASUREMENTS Blood was sampled 4‐hourly for 24 hours beginning at 1200 h. Oxytocin was measured in all patients and Β‐endorphin‐like immunoreactivity was measured in 15 patients.RESULTS A simple index was defined for comparing night‐time levels to daytime levels for both oxytocin and Β‐endorphin. In all cases more than 36 weeks gestation the index was positive for oxytocin (night‐time levels were higher) and in all cases the index was negative for Β‐endorphin (night‐time levels were lower). In the mid trimester women all values of the index for oxytocin were positive but in the Β‐endorphin group equal numbers demonstrated a positive or a negative index.CONCLUSIONS Reciprocal 24‐hour rhythms were demonstrated between oxytocin and Β‐endorphin; however, it is not clear whether this relationship is causal.