Funding ended

The purpose of the study is to evaluate the effect of a naturally occurring hormone, called Growth Hormone Releasing Hormone (GHRH) on the muscle, bone, and fat tissues of the body. GHRH stimulates the production of growth hormone (GH), which regulates the build up of many tissues in the body, including muscles and bones. Many elderly people have low levels of GH. The overall goal of this research is to determine the efficacy of GHRH to raise levels of GH and improve these body tissues. Healthy men and women age 65 and older will receive GHRH in four doses nightly for 12 weeks and assessed for changes in muscle strength, body mass, physical performance, and how the body uses sugar.

Although multiple factors appear to be associated with the functional deterioration of advanced age, decreases in muscle mass and strength (sarcopenia) are commonly seen in aging subjects and are major risk factors for subsequent disability. There are many potential causes of sarcopenia and functional impairment in the elderly, including medical conditions such as cardiovascular disease, altered mood, and sedentary lifestyle. Hyposomatotropism, or decreased activity of growth hormone (GH), is one factor that has been implicated.

GH is a major anabolic hormone that exerts important stimulatory effects on protein synthesis. Many of the peripheral tissue effects of GH are mediated by insulin-like growth factor 1 (IGF-1) produced systemically by the liver or locally in tissues in response to GH stimulation. IGF-1, in turn, regulates GH secretion by negative feedback mechanisms at the pituitary gland. Several investigators have shown that aging is associated with a decrease in spontaneous GH secretion and IGF-1 levels. GH levels decline by 14% for each decade after puberty. Reduction of GH release in aging is thought to be associated with an increase in somatostatin tone, decrease in hypothalmic GHRH output, and diminished response to GHRH. The fact that aging is accompanied by a decrease in protein synthesis leading to a loss of lean body mass and a gain in body fat suggests that a decrease in GH secretion may contribute to these changes. It has been hypothesized that restoration of GH level in the elderly to the levels observed in younger individuals may lead to improvements in body composition. GH may also increase slow wave (delta or deep) sleep in older adults.

Inclusion Criteria:

• Age of 65 years or older
• Fasting IGF-1 level <135ng/ml
• BMI 23-40 kg/m2
• Capable of giving informed consent

Exclusion Criteria:

• Diabetes mellitus or use of hypoglycemic agents
• Known coronary artery disease
• Liver disease, abnormal liver function tests (LRTs>2x upper limit of normal) or inflammatory bowel disease
• Renal insufficiency (serum creatinine > or = to 1.4 mg/dL)
• Hematocrit < 33% or > 50%
• History of malignancy < 5 years other than basal cell of the skin
• Chronic pulmonary disease or other systemic disorders which affect glucose hemostasis
• Use of growth hormone, corticosteroids, thiazide diuretics, estrogen supplements or androgen supplements
• Inability to perform strength or performance testing
• Uncontrolled hypertension (blood pressure >160/95
• NYHA Class III or IV heart failure
• Current smoking
• Alcohol use > or = to 30g/day
• Serious or unstable medical or psychological conditions that, in the opinion of the investigator, would compromise the subject's safety or successful participation in the study
• Participation in an investigational drug study within 6 weeks prior to screening visit
• Plan to change diet or exercise regimen during the study period