Endocrine Abstracts

Lymphocytic adenohypophysitis (LA) is a rare inflammatory disorder of the pituitary, probably auto-immune in origin, usually affecting young pregnant women. Clinical features resemble a pituitary adenoma but differing in the hierarchy of endocrine loss, preferentially destroying ACTH and TSH secreting cells. A useful diagnostic feature is pituitary enhancement with gadolinium on MRI.
A 39-year old female, with treated hypothyroidism, was referred to endocrinology out-patients with lethargy, weight gain and hirsuitism of the face and breasts. She had recently commenced hormone replacement therapy because of hot flushes and sweating. Clinical examination revealed a round plethoric face, hirsuitism of the chin, cheeks and breasts with thinning of the skin. Systemic examination, including visual field testing, was otherwise unremarkable.
Initial biochemistry revealed thyroid function consistent with thyroxine replacement (normal T4, suppressed TSH), low gonadotrophins (LH 1.7 units/litre, FSH 3.0 units/litre), low oestradiol (95 picomoles/litre) and testosterone (1.6 nanomoles/litre) but normal prolactin (253 nanomoles/litre). Androstenodione was slightly elevated at 10.9 nanomoles/litre. Cushing's syndrome was confirmed after failure of cortisol suppression (299 nanomoles/litre) on an overnight dexamethasone suppression test. Cortisol suppressed to 168 nanomoles/litre with high dose dexamethasone. ACTH was elevated at 21.9 picomoles/litre (2-11.3). Dynamic pituitary function testing revealed a good cortisol response (from 608 to 738 nanomoles/litre) and normal GHRH response (peak LH 33.8 units/litre, FSH 11.9 units/litre) but no GH response (1.1 to 5.7 units/litre). Pituitary MRI demonstrated an 8 millimetre pituitary tumour close to the optic chiasm enhancing with gadolinium. Metyrapone was commenced prior to transphenoidal excision. Biopsy from the surgical specimen demonstrated adenomatous tissue with ACTH positive cytoplasm with the remaining anterior pituitary tissue overshadowed by a dense lymphocytic infiltrate.
This is the only reported case of a combination of LA and an ACTH secreting adenoma. The charactersitic hierarchy of endocrine loss was masked by the concomitant ACTH secretion.