Williams Syndrome (WS) is a genetic syndrome with features that may include vascular stenoses, neuro-developmental changes, and a variety of endocrine and metabolic abnormalities, including impaired glucose metabolism and abnormal body composition. Approximately 75% of adults with WS have impaired glucose tolerance or diabetes on oral glucose tolerance testing (OGTT). In addition, clinical observations and preliminary data suggest increased overall body fat in these individuals, as well as a relative increase in fat deposition in the lower extremities. However, glucose and lipid metabolism in WS remain incompletely characterized. The purpose of the current study is to carefully describe glucose metabolism and lipid parameters in people with WS.

Inclusion Criteria

1. M or F age 14-70yo
2. Diagnosis of WS confirmed by FISH or chromosomal microarray (WS only)
3. Availability of a parent or guardian to participate in the consent process (all WS, and controls <18yo)

Exclusion Criteria

1. History of weight loss surgery or liposuction
2. Use of weight-lowering drugs
3. Positive urine pregnancy test (females only)
4. Obesity or abnormal fat distribution due to a known secondary cause (except WS) such as Cushing syndrome, HIV-infection, etc.
5. Known diabetes will preclude administration of the OGTT but not participation in other aspects of the study.

Children and adults with Williams Syndrome (WS), and "control" individuals without WS.