Insulin-like growth factors I and/or II are expressed in adrenal cells, and modulate
their proliferation and steroid hormone synthesis suggesting that they may function
as paracrine/autocrine factors. In some species, at least ACTH induces insulin-like
growth factor synthesis. Thus, these peptide growth factors mediate at least some
of the effects of ACTH on adrenocortical cell proliferation and differentiation. Human
fetal adrenals express insulin-like growth factor II gene abundantly and ACTH-dependently,
while in adult adrenals, the expression is low and no ACTH dependent regulation has
been demonstrated. Hormonally active adrenocortical carcinomas and virilizing adenomas
express insulin-like growth factor II gene abundantly. This phenomenon is associated
with reduced expression of two putative tumor suppressor genes (H19 and p57KIP2) locating on the same genomically imprinted locus on human chromosome 11p15.5. Tumor
necrosis factor-alpha belongs to the cytokines which modulate hypothalamic-pituitary-adrenal
axis. It is a potent inducer of ACTH secretion but, at the adrenal level, it seems
to mainly inhibit ACTH-induced steroidogenesis and also insulin-like growth factor
II expression. It is produced in adrenocortical steroidogenic cells in addition to
macrophages, which suggests that tumor necrosis factor-alpha may have some autocrine/paracrine
functions in the adrenal cortex.
Key words
Steroidogenesis - Adrenal - Imprinting - Cytokines - Tumor Suppressor - H19 - p57KIP2
