Endocrine Abstracts

A 73-year-old gentleman known to suffer from hypothyroidism was admitted to hospital with severe symptomatic hyponatraemia of 112 mmol/l. He was acutely confused with a GCS of 12/15. He was found to be in urinary retention with 650 ml residual urine post catheterisation. Initially, his serum sodium concentration improved on catheterisation and fluid restriction. The syndrome of inappropriate ADH secretion in the context of urine retention was initially suspected on the bases of a hypo-osmolar hyponatraemia, a urine concentration of >100 mOsmol/kg and urine Na > 40 mEq/l. His serum sodium started dropping again. A CT Trunk was performed which was normal. An MR Head was requested on account of persistent hyponatraemia. This revealed a large pituitary mass lesion measuring 18 × 17 × 18 mm (AP/COR/CC). This lesion filled the sella turcica and extended suprasellarly with mild superior displacement and impingement of the optic chiasm. The lesion was of intermediate - low signal intensity on T1-weighted image and intermediate signal intensity on T2 with another small 5 mm cystic lesion seen on the left. It enhanced moderately and homogeneously post contrast administration. On direct questioning, the patient denied any headaches or visual disturbances, lethargy, nausea or vomiting, poor appetite, weight loss or galactorrhoea. He complained of longstanding low libido, erectile dysfunction and lack of morning erections. Sampling of his pituitary profile revealed hypocortisolaemia, hypogonadotrophic hypogonadism and hyperprolactinaemia as seen below. He was already on adequate levothyroxine replacement therapy.

Pituitary Function Tests:

FSH: 1.3 U/l (0.7–11.1)

LH: 0.3 U/l (0.8–7.6)

TSH: 0.52 IU.ml (0.3–3)

Free T4: 13.46 pmol/l (11–18)

Prolactin: 508 mIU/l (45–375)

Growth Hormone: 0.19 ug/l (0–3)

Total testosterone: <0.69 nmol/l (4.47–29.5)

Cortisol am: 83 nmol/l (145–619)

Serum osmolality: 291 mOsmo/kg (282–300)

Urine osmolality: 728 mOsm/kg (50–1200)

IGF-1: 48 ng/ml (40–180)

Goldman’s perimetry test was within normal limits. The patient was started on hydrocortisone 10 mg – 5 mg – 5 mg on account of hypocortisolaemia. He was educated re the importance of lifelong steroids, sick day rules and usage of the hydrocortisone emergency pack. His serum sodium improved and remained normal. This gentleman has been referred for consideration of trans sphenoidal surgery and shall be followed up at our endocrine clinic with a six-monthly pituitary function test, Goldman’s perimetry and repeat MRI pituitary until his surgery is performed. Our case highlights a rarer presentation of a pituitary macroadenoma with hyponatraemia due to secondary adrenal insufficiency.