By
Liz Highleyman
Recombinant
human growth hormone (GH) has been studied as a treatment for wasting syndrome
and lipodystrophy in people with HIV/AIDS, but
it may also play a role in immune recovery, according to a study reported in the
March 3, 2008 Journal of Clinical Investigation.
Researchers
from the Gladstone Institute of Virology and Immunology, San Francisco General
Hospital, and the University of California at San Francisco conducted a prospective
randomized study examining the effects of GH on the immune system in HIV positive
adults.
As background, the study authors noted that GH is an "underappreciated
but important" regulator of T-cell development that can reverse age-related
declines in thymic production of immune cells (thymopoiesis) in rodents. The thymus,
a gland located behind the sternum, is the site of T-cell maturation in infancy,
but it typically undergoes involution or atrophy and fills with fat over time,
and its function declines by adulthood.
In the present small pilot study,
22 HIV-infected participants who had taken standard combination antiretroviral
therapy for at least 1 year (mean 3 years), but who had not experienced expected
CD4 cell increases, were assigned to receive either GH injections or not; after
1 year, the initially treated group stopped GH while the previously untreated
group started.
The researchers found that GH treatment was associated
with increased total thymus mass, but decreased fat. GH also enhanced thymic output,
as measured by an increase in the numbers of circulating total and naive (newly
produced) CD4 T-cells. The CD4 cell gain persisted for 1 year of follow-up after
GH was discontinued.
"These
findings provide compelling evidence that GH induces de novo T-cell production
and may, accordingly, facilitate CD4+ T-cell recovery in HIV-1-infected adults,"
the investigators concluded.
Further,
they added, "these randomized, prospective data have shown that thymic involution
can be pharmacologically reversed in humans, suggesting that immune-based therapies
could be used to enhance thymopoiesis in immunodeficient individuals."
While
this study offered "proof of principle" that GH might help spur CD4
cell recovery in people with HIV, the study authors urged caution, given the drug's
high cost and side effects including elevated blood glucose, swelling, and bone
and joint pain.
San Francisco General Hospital, San Francisco, CA; University
of California at San Francisco, CA; Gladstone Institute of Virology and Immunology,
San Francisco, CA.
3/14/08
Reference
LA
Napolitano, D Schmidt, MB Gotway, and others. Growth hormone enhances thymic function
in HIV-1-infected adults. Journal of Clinical Investigation 118(3): 1085-1098.
March 3, 2008.
