Endocrine and chronobiological effects of fasting in women.
OBJECTIVE
To determine whether fasting in women would suppress GnRH/LH drive in a high- versus low-gonadal steroid milieu.


METHODS
Case-control study.


METHODS
Academic clinical research center.


METHODS
Eleven eumenorrheic women and eleven women taking combined oral contraceptives.


METHODS
Seven of the eleven women in each group underwent an acute 72-hour fast. Blood samples were obtained at 15-minute intervals for 24 hours before the fast and during the last 24 hours of fasting.


METHODS
Twenty-four-hour profiles of LH, cortisol, and melatonin were assessed. Ovarian activity was tracked with estradiol and progesterone levels, and metabolic responses were gauged by measuring thyroid hormone and beta-hydroxy-butyric acid levels.


RESULTS
Fasting increased beta-hydroxy-butyric acid and reduced free thyronine. Fasting in the midfollicular phase had no effect on LH pulsatility or on FSH, estradiol, or subsequent luteal-phase progesterone levels. However, fasting elevated cortisol and resulted in a phase advance in melatonin secretion of 81 minutes in both the midfollicular and luteal phases.


CONCLUSIONS
Fasting in women elicited expected metabolic responses and apparently advanced the central circadian clock without compromising reproductive function.
Berga
S L
SL
Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. sberga@mail.magee.edu
Loucks
T L
TL
Cameron
J L
JL
D020155:3-Hydroxybutyric Acid / Q000097:blood; D000328:Adult; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology*; D016000:Cluster Analysis; D004958:Estradiol / Q000097:blood / Q000378:metabolism; D005215:Fasting / Q000378:metabolism / Q000502:physiology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000378:metabolism; D005498:Follicular Phase / Q000502:physiology; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism*; D008183:Luteal Phase / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D008550:Melatonin / Q000097:blood / Q000378:metabolism*; D010060:Ovulation / Q000502:physiology; D011374:Progesterone / Q000097:blood / Q000378:metabolism; D013970:Thyronines / Q000097:blood / Q000378:metabolism
D013970:Thyronines; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D008550:Melatonin; D020155:3-Hydroxybutyric Acid; D006854:Hydrocortisone