Endocrine Abstracts

Rathke’s cleft cysts (RCCs) are benign epithelium-lined cystic remnants of the embryonic Rathke’s pouch. We report a case of a previously fit and well 30-year-old lady with an incidental finding of a cystic pituitary lesion, discovered when she took part in a clinical trial as a normal volunteer. She had no history to suggest endocrine dysfunction.

Pituitary function tests showed prolactin 302 mU/l (ref <630), LH 2.2 U/l, FSH 4.9 U/l, oestradiol 252 pmol/l, IGF1 186 ug/l (65–350), TSH 1.51 mU/l (0.35–5.00), free T₄ 14.4 pmol/l (9.0-21.0), 0900 cortisol 154 nmol/l with 30 minute post-Synacthen cortisol of 493 nmol/l. MRI demonstrated a cystic lesion arising from the pituitary with a height of 14 mm extending into the suprasellar cistern, abutting the inferior optic chiasm. Serial MRI from 2009 to 2011 showed no change. Formal visual field testing was normal. A diagnosis of Rathke’s cleft cyst was made.

She fell pregnant in 2013. At 22 weeks gestation, a bitemporal hemianopia was noted. MRI demonstrated enlargement of the lesion to 16.5 mm in height with optic chiasmal impingement. She declined surgical intervention. Visual fields improved spontaneously towards the end of pregnancy. Post-partum MRI confirmed significant regression of the pituitary lesion with resolution of the mass effect on the optic chiasm. It was felt pre-emptive neurosurgical intervention prior to further pregnancy was not indicated. During a subsequent pregnancy in 2016, a temporal visual field defect was noted. The lesion now measured 22mm with optic chiasmal distortion. Transsphenoidal aspiration of the pituitary cyst was undertaken at 25 weeks gestation. Visual field defects resolved. Pituitary function remained intact.

RCCs are often discovered incidentally. Pituitary hormonal axes are altered in pregnancy, often leading to an increase in pituitary size and deterioration of pre-existing pituitary disease. This case highlights the challenges of managing pituitary lesions in pregnancy, and the importance of pre-pregnancy counselling, frequent review and visual field monitoring during pregnancy.