OBJECTIVE: To investigate the diurnal rhythm of estrogens in normally cyclic women during reproductive life. DESIGN: Multiple saliva sampling in normally cyclic healthy women during reproductive life at different phases of their menstrual cycles was carried out. METHODS: Salivary estradiol was measured by radioimmunoassay in samples collected every 2 h for 24 h from 15 normally cyclic healthy women during reproductive life during the menstrual phase, the late follicular/peri-ovulation phase, the early to mid luteal phase and the late luteal phase, respectively, of their menstrual cycles. The levels of salivary estradiol were analyzed by means of periodic regression. RESULTS: A daily biological rhythm of free estradiol was found after quantification with a nonlinear periodic regression model. The observed diurnal free estradiol rhythm consists of two major components: an asymmetrically peaked diurnal cycle and ultradian harmonics in the range of 6 to 12 h. The diurnal and ultradian rhythms were remarkably consistent throughout the menstrual cycle in terms of mesor (24 h mean level), peak width and amplitude. There was a tendency for the 24-h rhythm acrophases to converge in the early morning, while the acrophase of the menstrual phase occurred significantly later than in the late follicular/peri-ovulation phase. CONCLUSIONS: The diurnal rhythm of estradiol has a similar complex temporal organization for different menstrual phases. The menstrual cycle mainly modulates the acrophase of the diurnal rhythm.
AM Bao, RY Liu, EJ van Someren, MA Hofman, YX Cao and JN Zhou
EJ Van Someren, J Swart-Heikens, E Endert, PH Bisschop, DF Swaab, PJ Bakker, JA Romijn and E Fliers
BACKGROUND: Cranial radiation therapy (CRT) is required for successful treatment of a variety of brain tumours in childhood. OBJECTIVE: To investigate whether childhood CRT leads to altered sleep-wakefulness organization in adulthood, and to identify the determinants of such alterations. SUBJECTS AND METHODS: Subjective (questionnaires) and objective (actigraphy) measures of circadian rhythmicity and sleep were assessed in 25 individuals, 8-29 years after CRT for medulloblastoma (n=17) or other intracranial tumours (n=8), and in a group of 34 age-matched healthy individuals. Serum GH peak during insulin-induced hypoglycaemia and serum concentrations of prolactin and leptin (expressed per fat mass) were determined in the CRT group. RESULTS: The CRT group showed a markedly increased sleep duration (8.66 h, compared with 7.66 h in controls). In addition, the sleep-wake rhythm showed greater amplitude and less fragmentation, and less tolerance for alterations in the timing of sleep. Regression analysis showed both radiation dosage and neuroendocrine status to be determinants of sleep changes, suggesting that some of the alterations may be normalized with hormone supplementation. CONCLUSION: The present study shows that high-dose cranial radiation therapy in childhood is associated with objective and subjective changes in the sleep-wake rhythm in adulthood.