A 24-year-old woman presents with excessive thirst after a recent pituitary surgery. What is the most likely diagnosis?

The most likely diagnosis for the patient is central diabetes insipidus. This condition occurs when there is a deficiency of antidiuretic hormone (ADH), which is also known as vasopressin. The recent pituitary surgery in this case raises the likelihood of central diabetes insipidus because the pituitary gland is responsible for producing ADH. If the surgery has affected the gland either by removing or damaging the cells responsible for ADH secretion, it can lead to inadequate levels of this hormone, resulting in the kidneys being unable to concentrate urine. This leads to excessive production of dilute urine and subsequently causes excessive thirst, as the body attempts to compensate for the fluid loss.

In contrast, nephrogenic diabetes insipidus results from the kidneys' inability to respond to ADH, despite its normal or elevated levels. This condition is usually not triggered by pituitary surgery. Primary polydipsia is characterized by excessive thirst due to psychological or behavioral factors rather than a hormonal deficiency or renal issue, and it typically presents differently. Type 2 diabetes mellitus involves abnormal glucose metabolism and is not directly related to the body's handling of water and urine concentration. Therefore, the clinical context and recent surgical history strongly support the diagnosis of central diabetes insipidus