OK.. for a 5 year old thread.. I was liking the post topic so I researched this.. If I am understanding the below correctly, IGF-1 appears to increase hairloss. Anyone?
Occurrence of the male hair pattern is considered to be an
androgen-mediated process that depends on circulating testosterone and
dihydrotestosterone concentrations as well as on local conversion of
circulating testosterone to dihydrotestosterone in the skin (catalyzed
by the enzyme 5alpha-reductase). Our data confirm that there is a
stronger link between circulating testosterone and baldness, whereas
testosterone has a less obvious function in regulating the relatively
less androgen-dependent chest hair density. Androgen action stimulates
vellus hair to develop into coarse, pigmented hair on the body, but
prolonged exposure to androgen leads to regression to vellus hair and,
frequently, balding of the scalp. Little is known about the specific
function of SHBG or estradiol in male hair growth or hair loss, and
the results of our study, in this respect, must be replicated before a
credible conclusion can be reached. It is conceivable, however, that
high SHBG levels reduce the bioavailability of testosterone and thus
modulate its effect on hair patterning.
Our findings suggest that high levels of IGF-1 may be associated with
increased risk of vertex baldness. Substantial clinical evidence
appears to support this finding. The efficacy of testosterone
treatment on hair growth in children with hypopituitarism is enhanced
by GH, the effect of which is largely mediated through IGF-1. In
adults with hypogonadism, a combination of GH and gonadotropin
treatment improves testosterone secretion and reproductive function.
It has also been recently reported that GH treatment of GH-deficient
men increases hair scores in androgen-dependent areas. These effects
can be explained either by IGF-1 directly stimulating the androgen
receptor, or by IGF-1 increasing local 5alpha-reductase activity and
thus stimulating the local conversion of testosterone to
dihydrotestosterone. It has been postulated that IGF-1 modifies
post-receptor effectors of the androgen receptor, but this is not
clearly established.
[…]
In conclusion, we have found evidence that high levels of testosterone
and IGF-1 increase the likelihood of vertex baldness, whereas neither
of these hormones appears significantly or suggestively associated
with chest hair growth. SHBG is inversely associated with vertex
baldness as well as with chest hair growth, although the association
is significant only with respect to the latter. It appears that the
effect of SHBG, if genuine, could be explained by the involvement of
this compound in the modulation of bioavailability of testosterone.”
Hormones and hair patterning in men: A role for insulin-like growth
factor 1?
Lisa B. Signorello, Joanne Wuub, Chung-cheng Hsiehb, Anastasia
Tzonouc, Dimitrios Trichopoulos, Christos S. Mantzoros
Journal of the American Academy of Dermatology
Volume 40 • Number 2 • February 1999
Copyright 1999 American Academy of Dermatology, Inc.
“We observed that middle-aged and elderly men who reported modest to
substantial vertex balding at age 45 have lower circulating levels of
IGFBP-3 and higher levels of IGF-1 when controlling for IGFBP-3 level.
Growth factors are beginning to emerge as contributors to hair growth
and loss. IGF-1 is an abundant endocrine, paracrine, and autocrine
growth control factor that promotes proliferative activity in
epithelial and mesenchymal cells in numerous organ systems, including
the hair organ.”
[…]
“In the hair organ, IGF-1 is produced by connective tissue
constituents,10 and IGF-1 gene expression is enhanced by androgens.11
In androgen-responsive tissue, IGF-1 may act locally to positively
mediate the induction of 5-reductase by dihydrotestosterone.12 This
action of IGF-1 may be consequential for the development of balding
because conversion of testosterone to dihydrotestosterone in the scalp
by 5-reductase type 2 is essential for androgenetic alopecia.13
Indeed, oral 5-reductase type 2 inhibitors are now used to prevent
further hair loss and to induce hair regrowth in men with male pattern
balding.13 Experimental administration of the 5-reductase type 2
inhibitor finasteride results in diminished expression of IGF-1 and
its receptor and enhanced expression of IGFBP-3 in the rat prostate,
an androgen-dependent tissue.14 IGFBP-3 is the major carrier protein
that modulates the bioavailability of IGF-115 and thus may also be a
regulator of mediators of hair growth and cycle control. Our findings
are compatible with both the direct association of IGF-1 and the
modulating effect of IGFBP-3 on male pattern balding.”
