MON-LB46 Thyrotropinoma and Pregnancy

Thyrotropinomas (TSHomas) are rare pituitary tumours, comprising 1-2% of all pituitary adenomas. Thyrotropinomas in pregnancy are exceedingly rare and management of these in pregnancy can be challenging due to the potential for maternal and foetal harm. We report the case of a 35 year old woman who was found to have a pituitary macroadenoma on imaging whilst being evaluated for headaches and sinusitis. She had felt more stressed than usual but no other overt thyrotoxic symptoms. There were no visual field abnormalities or symptoms to suggest other endocrine hypo or hypersecretion. Pituitary MRI revealed a macroadenoma and biochemistry demonstrated raised free T4 24 pmol/L and free T3 6.8 pmol/L and inappropriately elevated TSH of 4.2 mIU/L, in keeping with secondary hyperthyroidism. She was scheduled for transsphenoidal (TSA) pituitary surgery, however on review she had naturally fallen pregnant. After a multi-disciplinary discussion, it was decided that surgery should be deferred and close observation be undertaken under the care of a multidisciplinary team. During the first half of pregnancy she suffered hyperemesis gravidarum with ongoing thyrotoxicosis but declined carbimazole. Her visual fields were normal throughout pregnancy. She delivered vaginally at 38 weeks, weight 3.395kg and had no malformations. Post birth was complicated by post-partum haemorrhage requiring multiple blood transfusions and intensive care. One week later after recovering, she was able to commence breastfeeding. She went on to TSA at 6months post partum with complete tumour resection. This case demonstrates the complexity of managing TSHomas in pregnancy and the potential cross reactivity of the early hCG rises with the already elevated TSH levels, likely exacerbating her hyperemesis gravidarum.