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A green kidney shape on paper releases a broad pale ribbon of water flowing to the right, with a small saffron hormone molecule resting beside it.

Diabetes Insipidus

~2 min readReviewed

In this topic5

  1. Antidiuretic Hormone Physiology
  2. Clinical Presentation of Diabetes Insipidus
  3. Hypothalamic (Central) Diabetes Insipidus
  4. Nephrogenic and Dipsogenic Diabetes Insipidus
  5. Diagnosis and Treatment of Diabetes Insipidus

Diabetes Insipidus

Diabetes insipidus (DI) is a syndrome defined by hypotonic polyuria, the passing of large volumes of dilute urine (urine more dilute than plasma), together with a failure to concentrate urine. Urine concentration depends on antidiuretic hormone (ADH), also called arginine vasopressin (AVP), acting on the kidney, so DI arises in one of two ways. Either there is too little ADH action, because the hormone is not secreted (central or hypothalamic DI) or because the kidney does not respond to it (nephrogenic DI); or there is a fluid intake so large that it suppresses ADH and overrides the kidney’s concentrating work (dipsogenic DI).

Routes through the topic

The idea that organises the topic is that urine concentration needs both enough ADH and a kidney that responds to it, with fluid intake as a third influence. A reader new to the subject can therefore go in order, starting with the hormone and ending with the diagnostic work-up. A reader who already knows the physiology can start at the form or the question of interest.

  1. Antidiuretic Hormone Physiology is the place to start. It explains where ADH is made and released, how its release is controlled by plasma osmolality, and how it concentrates urine in the collecting duct.
  2. Clinical Presentation of Diabetes Insipidus describes the syndrome as it appears at the bedside: the volume and dilution of the urine and the state of the plasma sodium.
  3. Hypothalamic (Central) Diabetes Insipidus covers the form in which too little ADH is secreted, its causes, above all pituitary surgery and the triple-phase course that can follow, and its epidemiology.
  4. Nephrogenic and Dipsogenic Diabetes Insipidus covers the two forms with normal ADH secretion: renal resistance to ADH, usually from lithium, and the excessive fluid intake of an abnormal thirst.
  5. Diagnosis and Treatment of Diabetes Insipidus follows the diagnostic pathway from the history and laboratory findings to the water deprivation test and plasma AVP measurement, and the treatment of each form. It is the note to use once the three forms are clear.