title: Temporal changes in testis weight during the past 50 years in Japan.
abstract: The ever-increasing presence of environmental toxicants and their disruptive effect on the reproductive systems of wildlife raises the question of possible damage to the human reproductive system. Using medicolegal data from over 20,000 Japanese men subjected to necropsy from 1948 to 1998, we investigated temporal changes in testis weight to find possible evidence of male reproductive disorders. We also carried out a histological examination of 747 testes collected from 1978 to 1998. Our detailed analyses of the development of testis weight over the past 50 years have revealed four clear phenomena: (i) the age at which testis weight reaches its maximum has decreased; (ii) peak weight showed a general increase until it started to decline in boys born after 1960; (iii) the decline-rate at which testis weight decreases after its peak has greatly accelerated; and (iv) the onset of increasing testis weight of boys has occurred at a progressively younger age. Our quantitative analyses of testis weight indicate the possibility of a subtle reproductive disorder in Japanese men, especially in those born after 1960. Together with the accelerated development and decline in testis weight during the past 50 years, the decline in peak weight might be indicative of a subtle interference of environmental toxicants with male reproductive organogenesis.
authors.affiliation: Department of Bioenvironmental Medicine, Graduate School of Medicine, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba, 260-8670, Japan. mori@med.m.chiba-u.ac.jp
authors.forename: Chisato
authors.initials: C
authors.lastname: Mori
authors.forename: Akihiko
authors.initials: A
authors.lastname: Hamamatsu
authors.forename: Hideki
authors.initials: H
authors.lastname: Fukata
authors.forename: Kyu-Bom
authors.initials: KB
authors.lastname: Koh
authors.forename: Noriko
authors.initials: N
authors.lastname: Nakamura
authors.forename: Sanae
authors.initials: S
authors.lastname: Takeichi
authors.forename: Takahiko
authors.initials: T
authors.lastname: Kusakabe
authors.forename: Takeshi
authors.initials: T
authors.lastname: Saito
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Morita
authors.forename: Shinichi
authors.initials: S
authors.lastname: Tanihara
authors.forename: Fujio
authors.initials: F
authors.lastname: Kayama
authors.forename: Masae
authors.initials: M
authors.lastname: Shiyomi
authors.forename: Jin
authors.initials: J
authors.lastname: Yoshimura
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sagisaka
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007248:Infertility, Male / Q000209:etiology / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D012098:Reproduction / Q000502:physiology; D013091:Spermatogenesis; D013737:Testis / Q000473:pathology* / Q000502:physiology; D013997:Time Factors