Heritability of reproductive hormones in adult male twins.
BACKGROUND
Proper functioning of the male reproductive axis depends on complex feedback systems between several hormones. In this study, the genetic contribution of various endocrine components of the hypothalamic-pituitary-testicular axis is evaluated and previously observed differences in FSH and inhibin B levels between mono- (MZ) and dizygotic (DZ) twins are re-investigated.


METHODS
Inhibin B, FSH, LH, sex hormone-binding globulin (SHBG) and testosterone levels were assayed in 128 adult males (20 MZ twin pairs, 7 single MZ twins, 10 DZ twin pairs, 27 single DZ twins and 34 siblings of twins, constituting 10 sibling pairs), aged 15.6-68.7 years. Hormone levels were compared across zygosity groups and heritability estimates were obtained using maximum likelihood variance component analysis.


RESULTS
Heritability estimates ranged from 56% (testosterone) to 81% (inhibin B and SHBG). For LH and FSH, the heritability was estimated at 68% and 80% respectively. No mean differences in hormone levels were observed across groups.


CONCLUSIONS
All measured hormones are highly heritable. A difference in the FSH-inhibin B feedback system between DZ twin males and MZ twin males could not be confirmed.
Kuijper
E A M
EA
Division of Reproductive Medicine, Department of Obstetrics and Gynaecology, VU University Medical Center, 1007 MB Amsterdam, The Netherlands. e.kuijper@vumc.nl
Lambalk
C B
CB
Boomsma
D I
DI
van der Sluis
S
S
Blankenstein
M A
MA
de Geus
E J C
EJ
Posthuma
D
D
D000293:Adolescent; D000328:Adult; D000368:Aged; D005640:Follicle Stimulating Hormone / Q000235:genetics*; D006801:Humans; D007265:Inhibins / Q000235:genetics*; D007986:Luteinizing Hormone / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D012738:Sex Hormone-Binding Globulin / Q000235:genetics*; D013739:Testosterone / Q000235:genetics*; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*
D012738:Sex Hormone-Binding Globulin; C422364:inhibin B; D013739:Testosterone; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone