| 1. |
- Malm, Gunilla, et al.
(författare)
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Reproductive function during summer and winter in Norwegian men living north and south of the Arctic circle.
- 2004
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 1945-7197 .- 0021-972X. ; 89:9, s. 4397-4402
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal, daylight-dependent variation in human spermatozoa counts, with lowest values during summer, has been suggested. To test this hypothesis, we performed a longitudinal study of semen quality and reproductive hormone levels in Norwegian men living north and south of the Arctic Circle. An ejaculate and a serum specimen were obtained both in summer and in winter from 92 volunteers in Tromsoe (69° north latitude) and 112 in Oslo (60° north latitude). Semen analyses were performed, and serum was assayed for FSH and inhibin B. The median spermatozoa concentration in Tromsoe after adjustment for abstinence period length was 49 × 106/ml in summer and 54 × 106/ml in winter. Corresponding values for Oslo were 59 × 106/ml and 54 × 106/ml. The seasonal differences in spermatozoa concentration were not statistically significant, nor were significant differences observed in median total spermatozoa count, semen volume, percentage progressive motile spermatozoa, or FSH. In Tromsoe, but not Oslo, inhibin B concentration was slightly, but significantly (P = 0.02) higher in winter than summer (229 ng/liter vs. 223 ng/liter).The length of the daylight period may have a slight impact on hormonal markers of spermatogenesis but does not cause substantial changes in spermatozoa numbers and motility.
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| 2. |
- Ruhayel, Yasir, et al.
(författare)
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Seasonal variation in serum concentrations of reproductive hormones and urinary excretion of 6-sulfatoxymelatonin in men living north and south of the Arctic Circle: a longitudinal study.
- 2007
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Ingår i: Clinical Endocrinology. - : Wiley. - 1365-2265 .- 0300-0664. ; 67:1, s. 85-92
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Tidskriftsartikel (refereegranskat)abstract
- bjective Seasonal variation in photoperiod or temperature may influence human reproductive biology. The present study evaluated whether seasonal changes occurred in the levels of reproductive hormones and the major melatonin metabolite, 6-sulfatoxymelatonin (aMT6s), in populations exposed to extreme variation in photoperiod and temperature. Design Two separate cohorts of Norwegian men were recruited from the general population in either of two locations: Tromso (69.5 degrees N, n = 92) or Oslo (60 degrees N, n = 112), located north and south of the Arctic Circle (66.5 degrees N), respectively. Measurements Four blood and 12-h overnight urine samples were obtained on separate occasions over a 12-month period, including during the photoperiod maximum and minimum. Serum concentrations of FSH, LH, testosterone (T), oestradiol (E-2), SHBG and the urinary excretion of aMT6s were assessed. Results Statistical analysis using generalized estimating equations indicated that LH levels were lowest during early winter in both locations (both P = 0.01). In Tromso, free T and E-2 concentrations peaked during early winter (P = 0.02 and 0.003, respectively). In Oslo, free T levels were lowest during early winter (P = 0.06) whereas E-2 levels were lowest during late summer (P < 0.001). Urinary aMT6s concentrations were lowest during early summer in Tromso and Oslo. Concentrations peaked during early winter in Tromso (P < 0.001) and during late winter in Oslo (P < 0.001). Conclusion LH levels exhibited similar changes in both locations, whereas the patterns of changes of the sex steroid concentrations differed, possibly indicating different underlying mechanisms. Excretion of aMT6s was lowest during early summer in both locations, indicating that the long natural photoperiod was sufficient to cause suppression of melatonin secretion. Whether these changes have any biological significance remains uncertain.
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