A 19 year old girl presented at 39 weeks gestation with headache and blurring of vision. MRI showed an enhancing pituitary mass measuring 1.2 cm maximum height, extending suprasellarly and distorting the optic chiasm. Visual field testing showed bilateral constriction. 0900 h cortisol was 502 nmol/l, thought to be relatively low for the stage of pregnancy and FT4 was 9.3 pmol/l suggesting TSH deficiency. Prolactin was appropriately raised for the gestational age at 4951 mU/l.
A diagnosis of probable lymphocytic hypophysitis was made. Given her advanced gestational age, pituitary surgery or biopsy was not thought to be appropriate. Regular hydrocortisone was started with high dose cover during labour. She was also given 1mg of cabergoline, based on the presumption that dopamine agonist treatment would stop the lactotroph hyperplasia and result in some tumour shrinkage. She delivered a healthy baby girl a week later and was asked not to attempt to lactate.
A month later repeat MRI showed regression of the pituitary mass to 8 mm and visual fields showed a substantial improvement. Prolactin was 411 mIU/l and FT4 was 12.9 pmol/l, implying recovery of the pituitarythyroid axis. The glucagon stimulation test showed a suboptimal peak cortisol at 429 nmol/l.
Consecutive MRI scans have shown a progressive reduction in the tumour size over subsequent months.
Insulin stress test 7 months post delivery showed a peak cortisol of 498 nmol/l and a peak GH of 1.8 μg/l. Gonadotrophins are normal and she is menstruating regularly. She takes hydrocortisone for intercurrent illness and remains asymptomatic from her GH deficiency.
Lymphocytic hypophysitis is a rare condition, thought to be autoimmune in origin, with a strong predilection for women in the peripartum period. It usually presents with enlarging pituitary mass and variable degrees of hypopituitarism. This case illustrates that conservative management of lymphocytic hypophysitis should be considered, as in some cases it may remit spontaneously.