Circadian rhythm of oestradiol: Impact on the bone metabolism of adult males

Background: Few studies have examined the variation in oestradiol with respect to age and circadian rhythm and the subsequent effects on BMD. Aim: Demonstrate the presence or absence of a circadian rhythm for oestrodial in older men and the integral role of concerted circadian rhythms of several factors including parathyroid hormone (PTH) in regulating biochemical markers of bone resorption and formation. Examine whether concentrations of both circulating total and bioavailable oestrogen in men differ with age and BMD. Design: Males were recruited: young men with normal BMD, older men with normal BMD and older men with osteoporosis. Methods: Subjects were hospitalized for a 25-hour period. Blood samples were obtained every 30 minutes. Hormone analysis results were plotted and reviewed. Results: Both total and bioavailable oestradiol concentrations were significantly lower in the older men than the young men (Total oestradiol: 34.5±4.4 pmol/L vs. 49.0±6.5 pmol/L, p<0.0001; Bioavailable oestradiol 16.7±2.2 pmol/L vs. 26.3±3.6 pmol/L, p