title: Reproductive function during summer and winter in Norwegian men living north and south of the Arctic circle.
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 degrees north latitude) and 112 in Oslo (60 degrees 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 x 10(6)/ml in summer and 54 x 10(6)/ml in winter. Corresponding values for Oslo were 59 x 10(6)/ml and 54 x 10(6)/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.
authors.affiliation: Fertility Center, Scanian Andrology Centre, Malmö University Hospital, SE 205 02, Malmö, Sweden.
authors.forename: Gunilla
authors.initials: G
authors.lastname: Malm
authors.forename: Trine B
authors.initials: TB
authors.lastname: Haugen
authors.forename: Trine
authors.initials: T
authors.lastname: Henrichsen
authors.forename: Cathrine
authors.initials: C
authors.lastname: Bjørsvik
authors.forename: Tom
authors.initials: T
authors.lastname: Grotmol
authors.forename: Thomas
authors.initials: T
authors.lastname: Saether
authors.forename: Johan
authors.initials: J
authors.lastname: Malm
authors.forename: Yngve
authors.initials: Y
authors.lastname: Figenschau
authors.forename: Lars
authors.initials: L
authors.lastname: Hagmar
authors.forename: Lars
authors.initials: L
authors.lastname: Rylander
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Levine
authors.forename: Aleksander
authors.initials: A
authors.lastname: Giwercman
mesh_terms: D000328:Adult; D001110:Arctic Regions; D006801:Humans; D007265:Inhibins / Q000097:blood; D008027:Light; D008137:Longitudinal Studies; D009664:Norway; D012621:Seasons; D013076:Sperm Count; D013081:Sperm Motility; D013091:Spermatogenesis
chemical_list: C422364:inhibin B; D007265:Inhibins