Effects of a growth hormone receptor antagonist on bone markers in acromegaly.
OBJECTIVE
Excess GH secretion, as occurs in acromegaly, is associated with abnormalities in bone turnover markers and bone mineral density (BMD). GH administration in GH deficient patients causes an increase in bone turnover. IGF-I mediates many of the metabolic actions of GH, although GH may have direct effects upon bone. In patients with acromegaly who are treated with a GH receptor antagonist, selective blockade of the GH receptor results in a decrease in circulating IGF-I levels in the majority of cases. We hypothesized that, in acromegaly, antagonism of GH receptors would result in a decrease in serum markers of bone turnover, including serum procollagen I carboxy-terminal propeptide (PICP), osteocalcin and N-telopeptide (NTx).


METHODS
Twenty-seven patients with acromegaly were enrolled as part of a multicentre 12-week trial of a GH receptor antagonist and were randomized to placebo (n = 7) or 10, 15 or 20 mg of pegvisomant (n = 20).


METHODS
Serum markers of bone turnover were determined at baseline and 12 weeks.


RESULTS
Baseline bone turnover markers were above the upper limit of normal in 23%, 19% and 32% of subjects for osteocalcin, PICP and NTx, respectively. During the 12-week placebo-controlled period, there were significant decreases in serum markers of bone formation, osteocalcin (-2.2 +/- 0.44 vs. placebo +0.01 +/- 0.39 nmol/l, P = 0.009) and PICP (-23.6 +/- 9.6 vs. placebo +18.1 +/- 12.8 micro g/l, P = 0.022) and a serum marker of bone resorption, NTx (-4.4 +/- 1.4, placebo +1.0 +/- 0.3 nm, P = 0.024).


CONCLUSIONS
Using a specific GH receptor antagonist, we found that normalization of IGF-I is associated with rapid reductions in markers of both bone formation and resorption, and that these processes remain coupled. These data confirm the highly significant effects of GH and IGF-I in modulating bone turnover. The independent contributions of GH and IGF-I to these effects and the long-term effects on BMD in this population remain to be determined.
Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
W P
WP
Fairfield
G
G
Sesmilo
L
L
Katznelson
K
K
Pulaski
P U
PU
Freda
S
S
Stavrou
D
D
Kleinberg
A
A
Klibanski
D000172:Acromegaly / Q000097:blood / Q000188:drug therapy / Q000503:physiopathology*; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000187:drug effects; D016723:Bone Remodeling / Q000187:drug effects*; D003094:Collagen / Q000097:blood; D024042:Collagen Type I; D005260:Female; D019382:Human Growth Hormone / Q000031:analogs & derivatives / Q000627:therapeutic use*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides / Q000097:blood; D011347:Procollagen / Q000097:blood; D011986:Receptors, Somatotropin / Q000037:antagonists & inhibitors*
D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; D011986:Receptors, Somatotropin; C052929:collagen type I trimeric cross-linked peptide; C042813:procollagen type I carboxy terminal peptide; D015675:Osteocalcin; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D003094:Collagen; C406545:pegvisomant