Related Experiment Video
Updated: Aug 9, 2026
Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures
Published on: November 11, 2016
Endocrine and chronobiological effects of fasting in women
S L Berga1, T L Loucks, J L Cameron
1Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. sberga@mail.magee.edu
Objective:
To determine whether fasting in women would suppress GnRH/LH drive in a high- versus low-gonadal steroid milieu.
Design:
Case-control study.
Setting:
Academic clinical research center.
Patient(S):
Eleven eumenorrheic women and eleven women taking combined oral contraceptives.
Intervention(S):
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.
Main Outcome Measure(S):
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.
Result(S):
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.
Conclusion(S):
Fasting in women elicited expected metabolic responses and apparently advanced the central circadian clock without compromising reproductive function.
Related Concept Videos
02:19Circadian Rhythms and Gene Regulation
01:22Hormonal Regulation of the Menstrual Cycle
At puberty, GnRH begins a pulsatile release pattern, which triggers the anterior pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The frequency and amplitude of GnRH pulses vary across the menstrual cycle, with faster pulses favoring LH release and slower pulses favoring FSH release.
01:28Menopause
01:19Factors Affecting Drug Biotransformation: Biological
Species differences: Variations in enzyme systems across species can cause disparities in drug metabolism. For instance, humans may metabolize certain drugs faster than rodents, altering therapeutic effects.
Strain differences: Genetic variations within a species can result in differing enzyme activity, impacting drug response and toxicity. For example, some mouse strains may...
01:15Chronopharmacokinetics: Circadian Rhythms and Influence on Drug Response
The time of drug administration is an important factor to consider, as it can influence the toxic dose of a drug. For example, a study conducted by Prins et al. in 1997 examined the effects of the timing of...
01:15Hypoglycemia and Glucagon