Insulin-like growth factor-1 (IGF-1) in some circumstances acts as the mediator of the metabolic effects of growth hormone. However, there is some evidence to suggest that GH and IGF-1 act differently in some metabolic pathways. We will study the differences between GH and IGF-1 when provided as therapy for growth hormone deficiency in adults. Specifically we will be assessing if either medication impacts cardiovascular risk factors and if so do they impact risk factors differently. Ten adult males ages 18-65 who are growth hormone deficient on stable medications and with stable MRI findings (in the event of a known pituitary mass) will be recruited for the study.