E-Poster Presentation ESA-SRB-ANZBMS 2021

A 45 year-old man presented after a fall with a 2-minute lie, one week of bifrontal headaches, myalgias and subjective fevers and was found to have profound hypo-osmolar hyponatraemia (serum sodium 104mmol/L). He had been prescribed Zopiclone and Panadeine forte one week prior. On examination, he was euvolaemic. There were no abnormal neurological signs apart from slowed mentation.

Biochemistry revealed an elevated urine osmolality (589mOsm/Kg) and sodium (65mmol/L) consistent with SIADH. A pituitary panel revealed hypogonadotropic hypogonadism and mild central hypothyroidism (Table 1). Creatine kinase was profoundly elevated (39,171 U/L). A rheumatological screen was unremarkable. A pituitary MRI revealed a slightly bulky pituitary gland with homogenous enhancement suggestive of lymphocytic hypophysitis (Figure 1).

His sodium incremented gradually with a 3% saline infusion and 1L fluid restriction and eventually normalised one week after discharge. His myalgias and CK resolved spontaneously. His thyroid and gonadal axis also normalised spontaneously two weeks later. A pituitary MRI five weeks later showed a normal pituitary gland.

Lymphocytic hypophysitis is rare. The most common presenting symptoms include headache, visual disturbance and symptoms resulting from loss of pituitary hormonal function.

Suggestive features on MRI to distinguish hypophysitis from adenomas include an enlarged pituitary with thickened stalk (Table 2).

The management of hypophysitis involves hormonal replacement of the affected axis. High dose glucocorticoids have been trialled in patients with severe symptoms (Table 3).  Surgery has been performed in cases with neurological symptoms or headache unresponsive to glucocorticoids.

SIADH has not previously been described in patients with primary hypophysitis. Other factors that could contribute to this included the use of opiates, and presence of pain.

Rhabdomyolysis has only been described in those with hypophysitis with concomitant cortisol deficiency. While there have been case reports of hyponatraemia as a cause of rhabdomyolysis, this has not been replicated in animal models.