Sexual Differentiation of the Bed Nucleus of the Stria Terminalis in Humans May Extend into Adulthood

 

Gonadal steroids have remarkable developmental effects on
sex-dependent brain organization and behavior in animals. Pre-
sumably, fetal or neonatal gonadal steroids are also responsible
for sexual differentiation of the human brain. A limbic structure
of special interest in this regard is the sexually dimorphic central
subdivision of the bed nucleus of the stria terminalis (BSTc),
because its size has been related to the gender identity disorder
transsexuality. To determine at what age the BSTc becomes
sexually dimorphic, the BSTc volume in males and females was
studied from midgestation into adulthood. Using vasoactive
intestinal polypeptide and somatostatin immunocytochemical
staining as markers, we found that the BSTc was larger and
contains more neurons in men than in women. However, this
difference became significant only in adulthood, showing that
sexual differentiation of the human brain may extend into the
adulthood. The unexpectedly late sexual differentiation of the
BSTc is discussed in relation to sex differences in developmen-
tal, adolescent, and adult gonadal steroid levels.

Key words: bed nucleus of stria terminalis; sexual differenti-
ation; plasticity; brain; adulthood; human