Absence of circadian rhythms of gonadotropin secretion in XXXX .

@entity1 @entity5815
CONTEXT: Diurnal rhythms of LH and FSH have been reported in normal @entity1 , but it is unclear whether these reflect underlying circadian control from the suprachiasmatic nucleus and/or external influences. OBJECTIVE: The aim of this study was to determine whether endogenous circadian rhythms of LH, FSH, and the glycoprotein @entity5815 ( @entity5815 ) are present in reproductive-aged @entity1 . DESIGN AND SETTING: Subjects were studied in the early follicular phase using a constant routine protocol in a Clinical Research Center at an academic medical center. SUBJECTS: Subjects were healthy, normal-cycling @entity1 aged 23-29 yr (n = 11). MAIN OUTCOME MEASURES: Temperature data were collected, and blood samples were assayed for LH, FSH, @entity5815 , and TSH. RESULTS: Core body temperature and TSH were best fit by a sinusoid model, indicating that known circadian rhythms were present in this population. However, the patterns of FSH, LH, and @entity5815 over 24 h were best fit by a linear model. Furthermore, there were no differences in LH and @entity5815 interpulse intervals or pulse amplitudes between evening, night, and morning. CONCLUSIONS: Under conditions that control for sleep/wake, light/dark, activity, position, and nutritional cues, there is no circadian rhythm of LH, FSH, or @entity5815 in @entity1 during the early follicular phase despite the presence of endogenous rhythms of TSH and core body temperature. These studies indicate that endogenous circadian control does not contribute to previously reported diurnal rhythms in reproductive-aged @entity1 and emphasizes the importance of environmental cues in controlling normal reproductive function.
