Time of onset of sperm production in boys.
D000293:Adolescent; D001827:Body Height; D001835:Body Weight; D002648:Child; D006801:Humans; D008297:Male; D011627:Puberty; D012741:Sexual Maturation; D013081:Sperm Motility; D013091:Spermatogenesis; D013094:Spermatozoa / Q000032:analysis; D013737:Testis / Q000502:physiology*; D014556:Urine / Q000032:analysis