Essential hypernatraemia, antidiuretic hormone and neurophysin secretion: response to chlorpropamide

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Abstract
An adolescent boy with essential hypernatremia, absent corpus callosum, mental retardation, hypodipsia and partial diabetes insipidus with inappropriate ADH regulation and secretion was studied regarding factors controlling ADH and neurophysin release. Persistent hyperosmolality was noted while on 100 meq Na intake daily. Endogenous vasopressin activity was demonstrated after prolonged H2O deprivation. Hypertonic saline infusion produced increased volumes but dilute urine. Aqueous pitressin increased urinary osmolality, decreased serum osmolality, urine flow rate and free H2O clearance. Stable H2O diuresis was induced by H2O loading and on normal saline infusion. Nicotine-stimulated neurophysin remained unexpectedly low and below the level of detectability when sampled during the physiologic studies; estrogen-stimulated neurophysin was elevated during estrogen stimulation, H2O loading and orthostasis procedures. Plasma vasopressin was suppressed with H2O loading but remained suppressed 90 min after tilt table testing. Impairment of the osmoreceptor mechanism is indicated; since the patient had a normal response of estrogen-stimulated neurophysin, that part of the neurohypophysis appears intact. Chlorpropamide was effective in alleviating the hyperosmolar state acutely and maintained normal osmolar concentrations during 2 yr of therapy.