Psychogenic polydipsia

Langlow JR, Alarcon RD. Trimipramine-induced neuroleptic malignant syndrome after transient psychogenic polydipsia in one patient. J Clin Psychiatry 1989 50(4) 144-5. 

Rhabdomyolysis occurred in two men, aged 21 and 42 years, taking clozapine (198,199). The first had no risk factors, but calcium-dependent potassium efflux, normally responsible for membrane hyperpolarization and muscle refractoriness, was severely impaired in his erythrocytes. The second had marked hyponatremia, due to psychogenic polydipsia, and developed a marked rise in creatine kinase activity (62 730 U/l) after correction of hyponatremia with hyperosmolar fluids. 

Wicki J, Rutschmann OT, Burri H, Vecchietti G, Desmeules J. Rhabdomyolysis after correction of hyponatremia due to psychogenic polydipsia possibly complicated by clozapine. Ann Pharmacother 1998 32(9) 892-5. 

HDI]), (2) deficient AVP action on the kidney (neplirogenic diabetes insipidus [NDI]), and (3) excessive water intake (psychogenic polydipsia). An osmotic diuresis may also produce polyuria and polydipsia. Uncontrolled diabetes mellitus with a high glucose load to the kidney is a common cause of an osmotic diuresis. 

Psychogenic or Primary Polydipsia. A chronic, excessive intalce of water suppresses AVP secretion and produces hypotonic polyuria. The polyuria and polydipsia are usually not as sustained as in HDI or NDI nocturnal polyuria also is less frequent. Psychogenic factors are most commonly associated with this disorder, but hypothalamic disease affecting the thirst center may be a cause. Drugs also can affect the thirst center and result in primary polydipsia. 

Overnight water deprivation test (Box 50-9) If the ratio of urine to plasma osmolality is <1.5 at the end of the test, primary polydipsia is unlikeiy. Measure plasma and urine osmolalities and plasma ADH concentrations at the end of the test use these relationships to differentiate normal, nephrogenic, or hypothalamic diabetes insipidus, and psychogenic polydipsia. If urine osmoiahty is <400 mOsm/kg at the end of the test, give 5 U of aqueous vasopressin subcutaneously. If urine osmolality increases >10%, hypothalamic diabetes insipidus is probable if urine osmolality does not increase, nephrogenic diabetes insipidus is highly probable. 

Figure 50-13 Retention of plasma vasopressin to osmolality. Regions I and 2 represent the normal reference interval and values seen in subjects with psychogenic polydipsia. Region 3 indicates central diabetes Insipidus, Region 4 is NDl, and Region 5 is SIADH. LD denotes the lowest detectable plasma vasopressin correlation with this assay. (Modified and abstracted from Zerbe RL, Robertson GL A comparison of plasma vasopressin measurements with a standard indirect test in the differential diagnosis of polyuria.

The differential diagnosis of euvolemic hypotonic hyponatremia also includes primary or psychogenic polydipsia. Patients with this... 

Hairprasad MK, Eisinger RP, Nadler IM, et al. Hyponatremia in psychogenic polydipsia. Arch Intern Med 1980 140 1639-1642. 

Psychogenic polydipsia, or compulsive water drinking (generally > 10 L/d), causes reduced serum sodium because of the excessive free water intake and because the kidney excretes sodium to maintain euvolemia. The urine sodium level may be elevated, but urine osmolality is appropriately low because the kidney is attempting to excrete the excess water and ADH secretion is suppressed. 

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