Change of the image of the posterior pituitary in a patient with mineralocorticoid-responsive hyponatremia of the elderly: comparison of findings before and after treatment

Hyponatremia with Loss of High Signal Intensity in the Posterior Pituitary Lobe on T1-weighted Magnetic Resonance Imaging

Herein, we report on an 82-year-old woman who presented with anorexia. The patient had hyponatremia with preserved urinary osmotic pressure. T1-weighted magnetic resonance imaging (MRI) showed a lack of high signal intensity (SI) in the posterior pituitary lobe. Based on the patient's high levels of N-terminal prohormone of brain natriuretic peptide (NT-proBNP), heart failure was suspected. The heart failure may have caused arginine vasopressin (AVP) secretion. The depletion of AVP secretory granules may therefore cause the posterior pituitary gland to disappear on T1-weighted MRI.

Mineralocorticoid responsive hyponatremia of the elderly: A systematic review

BACKGROUND

Mineralocorticoid responsive hyponatremia of the elderly (MRHE) is an emerging concept of hyponatremia in aged people. Diagnosis of MRHE requires exclusion of syndrome of inappropriate antidiuresis and adrenal dysfunction. Thus we aimed to evaluate the characteristics of all patients with suspected MRHE available for a review.

METHODS

We conducted a systematic review using MEDLINE and Google scholar. We included published case reports of adult patients diagnosed as MRHE, written by English and Japanese language. Serum and urine electrolytes as well as the levels of antidiuretic hormone (ADH), cortisol, plasma renin activity (PRA), and aldosterone were analyzed.

RESULTS

A total of 27 MRHE patients were identified in 9 reports. In these patients, average age was 79 years, median serum sodium was 117 mEq/L. The median levels of ADH, cortisol, PRA, and aldosterone were 0.9 pg/mL, 18.7 μg/dL, 0.37 ng/mL/h, and 39.6 pg/mL, respectively. Water restriction test was conducted in 7 patients. Random sample cortisol measurements did not exceed satisfactory levels to rule out adrenal dysfunction in four cases. No cases underwent low-dose adrenocorticotropic hormone stimulation test. Only 27 patients from 9 case reports in Japanese were eligible for inclusion in our study.

CONCLUSION

All published cases of MRHE as a cause of hyponatremia are described for the first time. In these cases, latent adrenal sufficiency might have been hidden and should have been excluded.

Severe hyponatremia in association with I(131) therapy in a patient with metastatic thyroid cancer

Hyponatremia is a common clinical problem that results from various causes. Hypothyroidism is known to be one of the causes of this disorder. We report a case of metastatic thyroid cancer presenting with severe hyponatremia in association with hypothyroidism induced by pretreatment of I(131) therapy, such as a low-iodine diet and withdrawal of thyroid hormone. Serum arginine vasopressin (AVP) was elevated and urine osmolality was higher than that of serum. Saline infusion and thyroid hormone replacement normalized serum sodium and AVP. Inappropriate secretion of AVP in hypothyroid state was thought to be one of the causes of this hyponatremia.

Five cases of severe hyponatremia in the elderly successfully treated with low doses of hydrocortisone

Hyponatremia is commonly defined as a serum sodium concentration of 135 mEq/L or less, which is reported to occur in 0.97-2.48% of hospitalized patients. Especially, in elderly patients, severe hyponatremia is sporadically developed without any complaints. Although a variety of causes of hyponatremia are documented, diagnosis of functional adrenal insufficiency is difficult because of a lack of the diagnostic criteria. In this case report, we present five cases of hyponatremia in the elderly, who were presumed to have functional adrenal insufficiency, successfully treated with low doses of hydrocortisone.