title: Testicular growth and development in puberty.
abstract: OBJECTIVE
  To describe pubertal testicular growth in humans, changes in testicular cell populations that result in testicular growth, and the role of testosterone and gonadotrophins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in testicular growth. When human data were not available, studies in nonhuman primates and/or rodents were used as surrogates.
  
  
  RESULTS
  Testicular growth in puberty follows a sigmoidal growth curve, with a large variation in timing of testicular growth and adult testicular volume. Testicular growth early in puberty is due to increase in Sertoli cell number and length of seminiferous tubules, whereas the largest and fastest growth results from the increase in the diameter of the seminiferous tubules first due to spermatogonial proliferation and then due to the expansion of meiotic and haploid germ cells. FSH stimulates Sertoli cell and spermatogonial proliferation, whereas LH/testosterone is mandatory to complete spermatogenesis. However, FSH and LH/testosterone work in synergy and are both needed for normal spermatogenesis.
  
  
  CONCLUSIONS
  Testicular growth during puberty is rapid, and mostly due to germ cell expansion and growth in seminiferous tubule diameter triggered by androgens. Pre-treatment with FSH before the induction of puberty may improve the treatment of hypogonadotropic hypogonadism, but remains to be proven.
authors.affiliation: Institute of Biomedicine, Department of Physiology, University of Turku, and Department of Paediatrics, Turku University Hospital, Turku, Finland.
authors.forename: Jaakko J
authors.initials: JJ
authors.lastname: Koskenniemi
authors.forename: Helena E
authors.initials: HE
authors.lastname: Virtanen
authors.forename: Jorma
authors.initials: J
authors.lastname: Toppari
mesh_terms: D000818:Animals; D005640:Follicle Stimulating Hormone / Q000627:therapeutic use; D006801:Humans; D007006:Hypogonadism / Q000188:drug therapy / Q000209:etiology; D008297:Male; D011627:Puberty / Q000187:drug effects / Q000502:physiology*; D012741:Sexual Maturation / Q000502:physiology*; D013091:Spermatogenesis / Q000187:drug effects / Q000502:physiology; D013737:Testis / Q000254:growth & development*; D013739:Testosterone / Q000378:metabolism
chemical_list: D013739:Testosterone; D005640:Follicle Stimulating Hormone