IDL, formed from the degradation of VLDL, transports a variety of triglyceride fats and cholesterol.  Disorders that cause a decrease in IDL (or<unk>  IDL) are few and are limited to an enzyme deficiency or genetic causes and medication side effects.
Low IDL causes
High IDL causes
Cystic fibrosis causes
Pulmonary hypertension causes
Ventricular septal defect causes
Asthma causes
Concussion causes
Renal agenesis causes