Severe hyponatremia caused by secondary adrenal insufficiency in a patient with giant pituitary prolactinoma

Syndrome of inappropriate antidiuretic hormone with recurrent giant cabergoline-resistant prolactinoma

A macro pituitary tumour or giant pituitary tumour is regarded as a rare causal factor in syndrome of inappropriate antidiuretic hormone (SIADH) cases. Previous reports have presented findings showing that blood flow insufficiency related to stress caused by an obstructive mass may lead to inappropriate secretion of arginine vasopressin. On the other hand, prolactin is known to influence water metabolism, and several cases of a macroprolactinoma or giant prolactinoma (PRLoma) in patients with SIADH have been reported. Nevertheless, few studies have examined such a relationship with SIADH and discussion of pathophysiological factors has been limited. The present report provides details of an elderly patient with SIADH in a chronic giant PRLoma. Of note, exacerbation of prolactin level accompanied the occurrence of SIADH. Findings obtained in this case suggest the possibility of development of SIADH in PRLoma cases due to more than only the effect of the mass.

Hyponatremia in the emergency department

Hyponatremia, defined as a serum sodium <135 mmol/L, is frequently encountered in patients presenting to the emergency department. Symptoms are often unspecific and include a recent history of falls, weakness and vertigo. Common causes of hyponatremia include diuretics, heart failure as well as Syndrome of Inappropriate Antidiuresis (SIAD) and correct diagnosis can be challenging. Emergency treatment of hyponatremia should be guided by presence of symptoms and focus on distinguishing between acute and chronic hyponatremia.

Nivolumab-induced hypophysitis causing secondary adrenal insufficiency after transient ACTH elevation

A 62-year-old man was referred to our department for elevation of plasma ACTH and cortisol levels during nivolumab administration for renal cell carcinoma. Although his ACTH and cortisol levels had been maintained within their reference ranges, they were elevated to 232.7 pg/mL and 21.9 μg/dL, respectively, after eight courses of nivolumab without any subjective symptoms or Cushing's sign. He was hospitalized for endocrinological investigation. ACTH and cortisol returned to their normal ranges (29.18 pg/mL and 11.4 μg/dL, respectively) in the early morning on day 1, but fell down sharply to 3.7 pg/mL and 1.6 μg/dL, respectively, in the early morning on day 2 without subjective symptoms or vital sign changes. Brain magnetic resonance imaging showed no abnormality in his pituitary gland. ACTH response to CRH was apparently normal, but cortisol did not respond to increased ACTH. A rapid ACTH stimulation test showed slightly reduced response of cortisol to exogenous ACTH (1-24). These findings and his clinical course suggested secondary adrenal insufficiency arising from nivolumab-induced hypophysitis. In previous reports, most cases of immune checkpoint inhibitor (ICI)-induced hypophysitis were diagnosed based on adrenal insufficiency symptoms or hyponatremia with low ACTH and cortisol. The ACTH elevation observed in the present case may reflect destruction of the pituitary gland, suggesting that this finding may be important for early detection of ICI-induced hypophysitis. Our case underlines the necessity of close monitoring for subsequent onset of adrenal insufficiency when ACTH elevation is observed during ICI administration.