Identification of sex hormone-binding globulin in the human hypothalamus

Gonadal steroids are known to influence hypothalamic functions
through both genomic and non-genomic pathways. Sex hormone-binding
globulin ( SHBG) may act by a non-genomic mechanism independent of
classical steroid receptors. Here we describe the
immunocytochemical mapping of SHBG-containing neurons and nerve
fibers in the human hypothalamus and infundibulum. Mass
spectrometry and Western blot analysis were also used to
characterize the biochemical characteristics of SHBG in the
hypothalamus and cerebrospinal fluid (CSF) of humans.
SHBG-immunoreactive neurons were observed in the supraoptic
nucleus, the suprachiasmatic nucleus, the bed nucleus of the stria
terminalis, paraventricular nucleus, arcuate nucleus, the
perifornical region and the medial preoptic area in human brains.
There were SHBG-immunoreactive axons in the median eminence and the
infundibulum. A partial colocalization with oxytocin could be
observed in the posterior pituitary lobe in consecutive semithin
sections. We also found strong immunoreactivity for SHBG in
epithelial cells of the choroid plexus and in a portion of the
ependymal cells lining the third ventricle. Mass spectrometry
showed that affinity-purified SHBG from the hypothalamus and
choroid plexus is structurally similar to the SHBG identified in
the CSF. The multiple localizations of SHBG suggest
neurohypophyseal and neuroendocrine functions. The biochemical data
suggest that CSF SHBG is of brain rather than blood origin.
Copyright (c) 2005 S. Karger AG, Basel