Circadian rhythm of melatonin in postmenopausal asthmatic women with hormone replacement therapy.

OBJECTIVE The aim of the study was to check if in postmenopausal women such a disease as asthma and use of hormone replacement therapy (HRT) influence daily melatonin (MEL) secretion. MATERIAL AND METHODS Studies were performed in 55 asthmatics (treated and not treated with glucocorticosteroids) and 20 healthy postmenopausal women (aged 48-60) before HRT and after 6 months of transdermal 17beta-estradiol and medroxyprogesterone acetate treatment (cyclical method). During the circadian study blood samples for the measurement of MEL were collected every 3 hours during the day. MEL concentrations were assessed with the use of RIA methods. Statistical analysis of the circadian rhythm was performed with the use of cosinor test according to Halberg et al. RESULTS Existence of daily rhythm of MEL secretion was shown in all studied groups, before as well as after HRT. A significant decrease of mesor and amplitude's rhythm was observed in the group of women with asthma treated with glucocorticosteroids (GC) before and after HRT use in relation to women not treated with GC and the control group. Secretion of MEL in these patients was lower at nocturnal hours. A significant decrease of mean daily MEL secretion in relation to values before HRT use was shown in all groups. CONCLUSIONS Asthmatic postmenopausal women treated with GC show lowered circadian secretion of melatonin as a consequence of lowering its secretion at nocturnal hours. Hormonal replacement therapy causes a decrease of daily melatonin secretion in healthy as well as asthmatic women, not disturbing circadian rhythm of this hormone's secretion.