Diabetes insipidus is a condition where people excretes excessive amounts of very dilute urine. It is caused by an endocrine abnormality. What abnormality would cause diabetes insipidus? How does this relate to the increased urination that occurs when people drink large amounts of alcohol?

Diabetes is a condition that increases urine production. Diabetes mellitus means sweet urine, and the urine is sweet because it contains large amounts of glucose. Diabetes insipidus basically means weak or insipid urine-the urine is very dilute. In ancient Greece, physicians differentiated the conditions by tasting the urine. Today we have different ways of differentiating them.
In diabetes insipidus the urine is dilutive because water is not being reabsorbed in the collecting duct. This is the result of inadequate secretion of antidiuretic hormone, which is responsible for inserting the water channels (aquaporins) in the collecting ducts. Without those water channels the capacity to reabsorb water is significantly reduced. More water stays in the body, so the blood volume increases. When the blood volume increases blood pressure increases, so low blood pressure is an important trigger for antidiuretic hormone release. Antidiuretic hormone also causes constriction of the blood vessels which is another way in which blood pressure can be increased. Because of this effect antidiuretic hormone is also known as vasopressin
vaso refers to blood vessels
pressin refers to increasing blood pressure