Differential Effects of rhGH vs. rhIGF-1 on Cardiovascular Risk Factors

Inclusion Criteria: * Adult male age 25-65 with documented growth hormone deficiency on stable doses x 3 months (at least) of any hormone replacement therapies and with stable MRIs x 2 years in the setting of a known pituitary mass. Exclusion Criteria: * Female gender * current GH use or GH use within three months of the study * diabetes * hypoglycemia * liver or kidney disease * use of drugs that could increase GH secretion (i.e. L-dopa) * alcohol or substance abuse * use of investigational drugs within four weeks of our study and use of supraphysiologic doses of steroids within the previous six months.