Modification of the circadian body temperature rhythm during the
luteal menstrual phase: the role of melatonin..
Cagnacci, Angelo, Renza Soldani, Gail A. Laughlin, Samuel S. C. Yen.
Department of Reproductive Medicine, University of California San
Diego, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0633
APStracts 2:0386A, 1995.
In early follicular phase (FP) women, the rise of melatonin at night
accounts for 40% of the nocturnal core body temperature (Tc) decline.
In seven normal cycling women the circadian rhythms of Tc and
melatonin of the FP were compared to those of the luteal phase (LP).
In addition, in both phases the Tc response to daytime melatonin
administration was investigated. Melatonin levels were comparable
during the two menstrual phases, but the nocturnal melatonin onset
was delayed by 90 minutes in the LP (p<0.01). This was
accompanied by a delay of the nadir of the Tc circadian rhythm
(p<0.002), a 0.3 degrees C elevation (p<0.005) of the mean
24-h value, and a 40% blunting (p<0.002) of the amplitude. This
attenuation of circadian Tc in LP women, was replicated in 2
estrogen-treated hypogonadal women by the administration of
medroxyprogesterone acetate (MPA). The daytime administration of
melatonin (2.5 mg) decreased Tc during the FP (p<0.01), but was
ineffective in the LP. Present data indicate that in LP, in
association with high progesterone levels, an attenuated and phase
delayed circadian Tc rhythm, may, in part, be due to a reduced effect
of melatonin.
Received 8 May 1995; accepted in final form 29 August 1995.
APS Manuscript Number A487-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.