Open Label Study to Analyze the Effect of Telotristat Ethyl on Weight Regulation/Gain

Inclusion Criteria: * Age ≥ 18 years. * Histopathologically confirmed diagnosis of a metastatic NET. * Documented history of carcinoid syndrome. * Currently receiving treatment with long-acting SSAs with a plan to initiate therapy with telotristat-ethyl as per standard of care. * ECOG performance status 0-1 and/or Karnofsky \>60%. * Greater than or equal to 3 month life expectancy. * Ability to understand and the willingness to sign a written informed consent. Exclusion Criteria: * Patients experiencing more than 12 watery BMs per day associated with volume contraction, dehydration, or hypotension, or showing evidence of enteric infection. * History of short bowel syndrome. * Clinically important baseline elevation in liver function tests. * Patients with known brain metastases should be excluded from this clinical trial because of their poor prognosis and because they often develop progressive neurologic dysfunction that would confound the evaluation of neurologic and other adverse events. * Malignant ascites requiring paracenteses. * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Bowel obstruction, partial, or total. * Pregnancy * Patients with unresolved grade 3/4 adverse effects of prior therapy at time of enrollment, other than diarrhea