a. This patient could have diabetes insipidus, which is a disorder of insufficient ADH activity. This can lead to frequent urination, and in this patient’s case frequent drinking. Diabetes insipidus has two forms, neurogenic or central DI or nephrogenic DI. Neurogenic DI is caused by inadequate secretion of ADH. It occurs when there is an interference with the ADH synthesis, transport, or release. It is most often associated with complications of closed head injuries. Neurogenic DI is also caused by hereditary disorders that affect ADH genes or damage to the pituitary gland. Nephrogenic DI is characterized by the improper response of the renal tubules to ADH. Acquired nephrogenic DI is closely associated with drugs and disorders that cause
