• Change in declarative memory, including total recall scores on three tests of memory and on dual task response time (RT), a test of executive function. [ Time Frame: Baseline, 10, 20, and 30 weeks ] [ Designated as safety issue: No ]
  

• Changes in other areas of cognitive function, including other tests of executive function, tests of lexical access, and tests of cognitive and perceptual-motor processing speed. [ Time Frame: Baseline, 10, 20, and 30 weeks ] [ Designated as safety issue: No ]
  

There is considerable and compelling evidence from both the animal and human literature that the actions of the somatotrophic hormonal axis (growth hormone releasing hormone/growth hormone/insulin-like growth factor I) have significant and predictable effects on cognitive function (memory and reasoning ability). A preliminary study has recently shown that five months of growth hormone releasing hormone (GHRH) treatment improves cognitive function in healthy older men and women; there is also preliminary evidence that supports the likelihood of a similar effect in individuals diagnosed with MCI.

The study sample will include 160 adults, ages 55-90, half of whom will be cognitively healthy normal adults and half of whom will meet diagnostic criteria for Mild Cognitive Impairment (MCI). Each of these groups will contain equal numbers of men and women. The treatment with GHRH will be twenty weeks in duration. In light of the documented interactions between estrogens and GHRH/GH/IGF-I, each of the two study arms will contain equal proportions of women not on estrogen replacement therapy (NERT) and women on oral estrogen replacement therapy (ERT). ERT women will maintain a regular steady dosage of estrogens for at least seven days preceding each assessment

Cognitive assessments to evaluate treatment-related changes in memory and thinking abilities, as well as blood collection to evaluate several biomarkers of interest, will be performed at baseline, 10 and 20 weeks of treatment, and ten weeks post-treatment. In addition there will be five medication and symptom monitoring visits during the treatment period.

The study hypotheses are:

H1: Healthy, cognitively normal older men and women treated with GHRH will show beneficial effects in cognitive function, including measures of memory, relative to placebo treated subjects.

H2: MCI patients treated with GHRH will show beneficial effects in cognitive function, including measures of memory, relative to placebo treated MCI patients.

H3: Changes in insulin-like-growth factor (IGF-I) will predict changes in cognition both for normal older adults and for MCI patients treated with GHRH.