Pituitary mass in pregnancy - unlikely to be an adenoma?
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A 21-year-old primigravida presented at 35 weeks gestation with a sudden onset of headache and blurred vision. She was normotensive with no proteinuria. Formal examination at the local eye hospital revealed bitemporal hemianopia and subsequent MRI indicated a pituitary mass with suprasellar extension and chiasmal compression. The lesion was heterogeneous in signal characteristics with areas of cystic change posteriorly. The initial endocrine assessment confirmed an elevated prolactin level (3876 mU/L; range 29-452), which was thought to be due to a combination of pregnancy, prolactin production by a pituitary adenoma, and/or compression of the pituitary stalk.

The working diagnosis by the obstetricians was that of pituitary macroadenoma and, given the raised prolactin, she was commenced on Bromocriptine. Although her vision improved a little the Bromocriptine was poorly tolerated and therefore abandoned a few weeks later. After multidisciplinary discussions between the anesthetist, endocrinologist, and obstetrician, labor induction was agreed upon. Pain relief was provided by an epidural and labor was covered with hydrocortisone in case she had pituitary ACTH deficiency. She gave birth to a healthy female infant of normal birth weight, by spontaneous vaginal delivery.

Seven weeks post-partum, her visual field defects persisted and a repeat MRI scan confirmed that the suprasellar lesion was unchanged in size or nature. Repeat endocrine assessment now revealed normal serum prolactin (290 mU/L) but confirmed partial ACTH deficiency. Given the ongoing visual deficits, following joint consultation between the endocrinologists and neurosurgeons, surgical decompression was deemed appropriate.

Endoscopic transsphenoidal resection of a relatively firm pituitary lesion with central areas of cystic change was undertaken. Post-operative recovery was uneventful other than for transient diabetes insipidus. Her visual field deficits resolved and post-operative MR confirmed satisfactory decompression of the optic chiasm. The histopathological assessment confirmed a diffusely inflamed pituitary gland with dense chronic inflammatory cell infiltrates, notably histiocytes (CD68 immunopositive) and lymphoid follicles with germinal centers (immunopositivity for CD3, a marker for T lymphocytes and CD20, a marker for B lymphocytes). Overall, these findings were consistent with a diagnosis of lymphocytic hypophysitis.

Following surgery, the patient retained a regular menstrual cycle and conceived spontaneously one year later. She continued on the hydrocortisone throughout the subsequent pregnancy, which progressed to a spontaneous vaginal delivery (labor supported with additional corticosteroid cover) of a male infant. She remains well and plans to have a Progesterone Secreting Intrauterine System (Mirena Coil) inserted soon. There was no recurrence of her previous lymphocytic hypophysitis.