Endocrine Abstracts

An 85 year old woman presented with generalised fatigue.Clinical examination was unremarkable but her biochemistry showed low sodium level of 112 millimoles per litre ( NR : 135-145 ).
Investigations were suggestive of Syndrome of Inappropriate Antidiuretic Hormone Secretion ( SIADH ) with low serum osmolality , high urine osmolality and high urinary sodium .
Further investigations were normal including renal function , short synacthen test , chest x-ray and CT scan of the head .
However the rest of her hormonal profile showed low TSH , low free T4 , low free T3 as well as low FSH and low LH levels but normal prolactin.
MRI scan of the pituitary gland showed an 'Empty Sella ' .
She did have a poor response to fluid restriction alone but started to respond gradually when Demeclocycline was added with a small dose of Thyroxine .
Discussion : An ' Empty Sella ' is sometimes reported on pituitary imaging. This is sometimes due to a defect in the diaphragma and extension of the subarachnoid space ( cisternal herniation ) or may follow spontaneous infarction of a pituitary tumour. All or most of the sella tursica is devoid of apparent pituitary tissue which is eccentrically placed and flattened against the floor or roof of the fossa . Pituitary function is usually normal . However , Empty Sella remains one of the causes of Hypopituitarism .
This patient with empty sella and partial anterior hypopituitarism was expected to have cranial diabetes insipidus with Antidiuretic hormone deficiency , however she did present the other way with inappropriately high antidiuretic hormone secretion and low sodium.
This would alert the Endocrionologist while investigating low sodium and SIADH to think about possible Empty Sella and possible underlying partial hypopituitarism .