1 Department of Pathophysiology, Medical Faculty and 3 Institute of Clinical and Nurse Sciences, Faculty of Health Sciences University of Pécs and 2 Department of Obstetrics and Gynaecology Baranya County Teaching Hospital, Pécs, Hungary
4 To whom correspondence should be addressed at: Department of Pathophysiology, Faculty of Medicine University of Pécs, H-7624 Pécs, Szigeti u. 12. Hungary. e-mail: janos.garai{at}aok.pte.hu
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: equinox/human menopause/menstrual cycle/seasonal change
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Nevertheless, only scarce data are available to date about the exact nature of environmental and/or lifestyle determinants of the menopause syndrome. Hence we propose that more detailed studies are needed to obtain knowledge that may aid us in implementing innovative approaches in its treatment.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Time divisions, such as hours of a day or months (and seasons) of a year, represent a circular scale of measurement. Since the widely used methods for scalar data are unable to analyse circular distributions properly (Zarr, 1984), the
2 goodness of fit test was chosen to analyse data obtained in our study.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Our sample shows a conspicuous seasonality in cessation of menstrual bleeding, with a higher peak after the vernal (spring) equinox and a lower one after the autumn equinox (Figure 1, Table I). Considering the four seasons in this sample, the events observed are not scattered uniformly all year round according to the 2 goodness of fit test for circular data. (P < 0.005;
2 = 13.294; df = 3).
|
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Melatonin is generally accepted as a signal that transmits length of day information to different physiological processes, although the underlying mechanisms may vary. Even in humans, the intricate relationship of melatonin and the menstrual cycle is well documented (Cagnacci and Volpe, 1996). Melatonin binding is found in the ovaries (Ayre and Pang, 1994
), and ovarian steroid hormone production is influenced by melatonin (Brzezinski et al., 1992
). The harmony of these links seems to become disrupted in parallel with a decrease of melatonin levels in early peri-menopause (Vakkuri et al., 1996
).
In view of these data and our findings, a plausible scenario for onset of menopause might be the following: cessation of ovarian function is a process from regular toward irregular control and is not merely due to the exhaustion of the gonadal tissue in its capacity to produce developing follicles that provide an adequate hormone supply. Rather, it can be perceived as a loss of ability for cyclic renewal of ovarian reproductive competence governed normally by several endogenous and exogenous factors affected by climatic conditions (e.g. length of day, temperature, humidity, etc.). A periodicity of either 12 or 6 months length seems to be operative in this regimen at least at the latitude and climate observed in this study. Due to imbalance of these factors in pre-menopause, the process eventually culminates to a point where it stumbles into a non-recoverable state, i.e. ovarian failure. Length of day is surely only one of several factors to be considered here. Moreover, as we have learned recently, melatonin might not be the only agent of circadian phototransduction (Campbell and Murphy, 1998).
![]() |
Acknowledgements |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Brzezinski A, Fibich T, Cohen M, Schenker JG and Laufer N (1992) Effects of melatonin on progesterone production by human granulosa lutein cells in culture. Fertil Steril 58,526529.[Medline]
Cagnacci A and Volpe A (1996) Influence of melatonin and photoperiod on animal and human reproduction. J Endocrinol Invest 19,382411.[Medline]
Campbell SS and Murphy PJ (1998) Extraocular circadian phototransduction in humans. Science 279,396398.
Nozaki M, Mitsunaga F and Shimizu K (1995) Reproductive senescence in female Japanese monkeys (Macaca fuscata): age- and season-related changes in hypothalamicpituitaryovarian functions and fecundity rates. Biol Reprod 52,12501257.[Abstract]
Shideler SE, Gee NA, Chen J and Lasley BL (2001) Estrogen and progesterone metabolites and follicle-stimulating hormone in the aged macaque female. Biol Reprod 65,17181725.
Vakkuri O, Kivelä A, Leppäluoto J, Valtonen M and Kauppila A (1996) Decrease in melatonin precedes follicle-stimulating hormone increase during perimenopause. Eur J Endocrinol 135,188192.[Medline]
Zarr JH (1984) Biostatistical Analysis. Prentice-Hall, Englewood Cliffs, NJ.
Submitted on January 9, 2004; accepted on March 19, 2004.