Osmoregulation of plasma vasopressin in three cases with adrenal insufficiency of diverse etiologies

Arginine vasopressin-independent mechanism of impaired water excretion in a patient with sarcoidosis complicated by central diabetes insipidus and glucocorticoid deficiency

A 28-year-old man was admitted to our hospital because of reduced livido and increased fatigability. Four months before admission, he noticed polyuria, which was gradually relieved by admission. Magnetic resonance imaging revealed enhancing lesion centrally in the pituitary stalk. Biopsy from the skin revealed noncaseating granuloma composed of epithelioid cells, and a diagnosis of sarcoidosis was made. Although plasma arginine vasopressin (AVP) was undetectable after administration of hypertonic saline, urinary output was within normal range (1.5 to 2.2 L/day). The urine osmolality became above plasma levels during the hypertonic saline test. Hormonal provocative tests revealed partial glucocorticoid deficiency. Soon after the glucocorticoid therapy was begun, moderate polyuria (from 3.5-4.0 liters daily) occurred. At this time, plasma AVP was undetectable, and urine osmolality was consistently below plasma levels during the hypertonic saline test. In conclusion, we showed in human study that masked diabetes insipidus could be mediated by AVP-independent mechanisms.

Fatal and near-fatal encephalopathy with hyponatraemia in two siblings with fluticasone-induced adrenal suppression

AIM

To document previously unreported acute effects of adrenal insufficiency.

METHODS

We describe two siblings who presented acutely with hyponatraemia and cerebral oedema following prolonged treatment with high dose inhaled fluticasone.

RESULTS

A girl aged 5.5 years presented with vomiting, headache, visual impairment and seizures. She was hyponatraemic but not hypoglycaemic. Her conscious level continued to deteriorate and she died, post mortem examination showing small adrenal glands and cerebral oedema. Four weeks later her 7-year-old brother presented with similar symptoms. Assessment showed hyponatraemia with cerebral oedema. His illness responded to intensive care. A diagnosis of adrenal insufficiency was made retrospectively in both cases. The siblings had been receiving Fluticasone propionate (FP) in doses of up to 2000 microg/day for several years.

CONCLUSION

We believe that the hyponatraemia and cerebral oedema was related to cortisol deficiency, leading to impaired excretion of water. We emphasize the need for careful cerebral monitoring in acute adrenal insufficiency presenting with impaired consciousness.

Regulation of arginine vasopressin in the syndrome of inappropriate antidiuresis

The syndrome of inappropriate antidiuresis (SIAD) is a disorder of sodium and water balance characterized by hypotonic hyponatremia and impaired water excretion in the absence of renal insufficiency, adrenal insufficiency, or any recognized stimulus for the antidiuretic hormone arginine vasopressin (AVP). Hyponatremia is primarily a result of excessive water retention caused by a combination of excessive intake and inappropriate antidiuresis. It is sometimes aggravated by a sodium deficiency caused by decreased intake and/or a secondary natriuresis triggered by and largely corrective of the increase in extracellular volume. Hence, there is neither edema nor signs of hypovolemia. Inappropriate antidiuresis is usually due to administration or endogenous production of AVP or another vasopressin receptor agonist such as desmopressin. Endogenous production can be either ectopic (from a tumor) or eutopic (from the neurohypophysis). The latter apparently is induced by a wide variety of diseases, drugs, or injuries and is divisible into 3 different types of abnormal AVP release during hypertonic saline infusion: high, erratic fluctuations unrelated to increases in plasma sodium (type A); a slow constant "leak" that is also unaffected by increases in plasma sodium (type B); and rapid progressive increases in plasma AVP that correlate closely with plasma sodium as it rises toward the normal range (type C or "reset osmostat"). In 5% to 10% of patients, there is no demonstrable abnormality in the osmoregulation of AVP (type D) and the cause of inappropriate antidiuresis is unclear. In some children it appears to be due to an activating mutation of the V2 receptor (V2R). In other patients, it may be due to abnormal control of aquaporin-2 water channels in renal collecting tubules or production of an antidiuretic principle other than AVP. These different types of osmoregulatory dysfunction underlying SIAD may result in marked differences in clinical presentation or response to therapy with fluid restriction, hypertonic saline infusion, or vasopressin antagonists.

The human hypothalamo-neurohypophysial system in health and disease

The present paper reviews the changes observed in the human supraoptic (SON) and paraventricular (PVN) nuclei, and their projections to the neurohypophysis, median eminence and to other brain areas in health and disease.