DIABETES insipidus has long been identified with lesions of the neurohypophysis or its afferent neutosecretory cells originating in the supraoptic and paraventricular nuclei of the hypothalamus (Fisher, Ingram and Clark, 1938; Scharrer and Scharrer, 1954; Bargmann and Scharrer, 1951). Interruption of this hypothalamo-hypophyseal system is caused by tumours, infections, trauma and vascular disease, in about half the reported cases; the others are called idiopathic (Blotner, 1958), about 1-3 per cent being hereditary (Forsmann, 1945). Only two idiopathic and two hereditary cases have been reported in which the hypothalamus has been studied histologically (Blotner, 1958; Hanhart, 1940; Gaupp, 1941). The present report concerns two additional cases of diabetes insipidus, one hereditary and one idiopathic, in both of which a marked reduction in the number of neurons in the supraoptic and paraventricular nuclei was found. This decrease in neurons known to secrete antidiuretic hormone (ADH)(Hild, 1956; Anderson and Haymaker, 1962) correlates well with the history of diabetes insipidus in these patients.

A deficiency of ADH is generally accepted as being responsible for the polyuria and thirst of diabetes insipidus. In addition to ADH, oxytocin is also formed in the supraoptic and paraventTicular nuclei and is considered to be responsible for milk ejection and breast-feeding (Gale and Larsson, 1963). In view of the loss of neurons found in these nuclei, the ability of two members of the family with hereditary diabetes insipidus to breast-feed their children suggests that in the human oxytocin either is not necessary for milk ejection or is secreted by other hypothalamic neurons.