title: Free and bioavailable fractions of sex steroids may influence bones in young men, depending on age and oestradiol level.
abstract: BACKGROUND
  Longitudinal bone growth ceases by the end of puberty, and it is thought to be a result, in both sexes, of increased pubertal oestrogen serum concentrations. Since peak bone mass is achieved by the third decade of life or later, the aim of this study was to relate sex steroid hormones and sex hormone binding globulin (SHBG) levels to bone quality in men during their third and fourth decades of life.
  
  
  METHODS
  Eighty men, healthy volunteers aged between 18 and 39 years, were subjected to an interviewer-administered questionnaire, body mass index (BMI) measurement, blood sample and calcaneal quantitative ultrasound (QUS) (Hologic-SAHARA). Blood was assessed for testosterone (T), oestradiol (E2), dehydroepiandrosterone sulfate (DHEAS), SHBG, luteinising hormone (LH) and follicle stimulating hormone (FSH). Free and bioavailable T and E2 levels were calculated knowing SHBG and albumin levels.
  
  
  RESULTS
  While T, E2, DHEAS, LH and FSH levels were not related, free and bioavailable fractions of T and E2 were positively associated with QUS readings. SHBG level was associated negatively. After dichotomisation for age, the associations remained significant only for younger subjects (18-30 years, n = 47). After adjustment for other co-variants, only SHBG in younger subjects retained its negative association with QUS. Older subjects (31-39 years, n = 33) revealed higher BMI and lower serum concentrations of total (-17 %), free (-18.5%) and bioavailable (-22.5%) levels of E2 than younger subjects.
  
  
  CONCLUSIONS
  Free and bioavailable fractions of sex steroids may influence bones in young men, depending on age and E2 level.
authors.forename: Dorota
authors.initials: D
authors.lastname: Szyska-Skrobot
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Marchlewska
authors.forename: Renata
authors.initials: R
authors.lastname: Walczak-Jędrzejowska
authors.forename: Elżbieta
authors.initials: E
authors.lastname: Oszukowska
authors.forename: Eliza
authors.initials: E
authors.lastname: Filipiak
authors.forename: Piotr
authors.initials: P
authors.lastname: Kula
authors.forename: Ryszard
authors.initials: R
authors.lastname: Mężyk
authors.forename: Aldona
authors.initials: A
authors.lastname: Kowalska
authors.forename: Ryszard
authors.initials: R
authors.lastname: Jaszewski
authors.forename: Jolanta
authors.initials: J
authors.lastname: Słowikowska-Hilczer
authors.affiliation: krzysztof.kula@umed.lodz.pl.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Kula
mesh_terms: D000328:Adult; D000375:Aging / Q000097:blood; D001682:Biological Availability; D015992:Body Mass Index; D002111:Calcaneus / Q000502:physiology*; D004958:Estradiol / Q000097:blood*; D012739:Gonadal Steroid Hormones / Q000097:blood*; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D008297:Male; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D013739:Testosterone / Q000097:blood; D055815:Young Adult
chemical_list: D012739:Gonadal Steroid Hormones; D012738:Sex Hormone-Binding Globulin; D013739:Testosterone; D004958:Estradiol; D013006:Growth Hormone