An assessment of posterior pituitary function in patients with Sheehan's syndrome

Antidiuretic hormone (ADH) function was assessed in a group of 16 patients with Sheehan's syndrome and 17 controls. All patients were on adequate cortisone and thyroxine replacement therapy before testing. During the dehydration test the patients revealed an impairment of ADH function. The maximum urine osmolalities and the urine-plasma osmolality ratios were significantly lower in the patients with Sheehan's syndrome compared to controls (maximum urine osmolalities 633 +/- 38 (SEM) and 873 +/- 29 (SEM) mOsm/kg, respectively, P less than 0.001; urine-plasma osmolality ratios 2.15 +/- 0.14 (SEM) and 3.01 +/- 0.10 (SEM), respectively, P less than 0.001). Plasma osmolalities were significantly higher in the patients (296.1 +/- 1.2 (SEM) and 290 +/- 0.9 (SEM), respectively, P less than 0.001). The patients took a longer period to achieve these maximum urine osmolalities. Three of the patients with Sheehan's syndrome were diagnosed as having diabetes insipidus since their maximum urine osmolalities were below 600 mOsm/kg and following desmopressin all three had an increment in urine osmolality which exceeded 9%. In addition these three patients had a maximum urine-plasma osmolality ratio below 1.9. Thus, it appears the patients with Sheehan's syndrome have an impairment of ADH function which manifests in some as diabetes insipidus.