Use of human unacylated ghrelin (UAG, also called des-octanoyl ghrelin) to study physiology in healthy subjects. The proposed research is an investigator-initiated study funded by the National Institutes of Health designed to examine the effect of physiologic levels of UAG on the regulation of glucose homeostasis as well as beta cell function.

Inclusion Criteria:

1. Apparently healthy men and women. Only premenopausal women who are using an adequate method of contraception at Screening and who agree to continue the contraception during the study will be included. Male subjects do not need to use on birth control.
2. Ages between 18 and 50 years, inclusive.
3. BMI between 18.5 and 29.9 kg/m2, inclusive

Exclusion Criteria:

1. History or clinical evidence of impaired fasting glucose or impaired glucose tolerance or diabetes mellitus, myocardial infarction, history or symptoms of congestive heart failure, history of cancer or anorexia nervosa, history or active liver or renal disease (AST or ALT >2x upper limits of normal, calculated glomerular filtration rate [GFR] <60).
2. A baseline resting systolic blood pressure of less than 100 mm Hg.
3. History of growth hormone deficiency or excess disorders (acromegaly, pituitary gigantism, panhypopituitarism); history of adrenal insufficiency or Cushing's disease/syndrome; history of neuroendocrine tumors.
4. Anemia defined as hematocrit <33%.
5. Use of medications that alter insulin sensitivity: niacin, glucocorticoids, metformin, thiazolidinediones, exenatide, or atypical anti-psychotics.
6. Pregnancy or lactation.
7. BMI <18 kg/m2 or BMI >30 kg/m2; fasting plasma glucose >100 mg/dl and/or 2 hr plasma glucose >140 mg/dl on a 75 g oral glucose tolerance test.
8. Electrocardiogram (ECG) abnormalities: specifically, myocardial ischemia, previous myocardial ischemia, atrial fibrillation, second or third degree heart block and complete right or left bundle branch block.
9. Females who are on progesterone-only contraception and those who have irregular menses.