Endocrine Abstracts

Presentation: A 20 year old student was brought to the Emergency Department with a 13 day history of heavy menstrual bleeding. On the day of her admission she had collapsed. On admission, she was noted to be pale with severe postural drop (70 mm Hg).

Investigations: Haemogobin: 46 g/l. Blood film showed an iron-deficient picture. eGFR: 54ml/min/1.73m2. Creatinine: 124 μ mol/l. Free T4: <5.3 pmol/l. TSH: >500 mU/l. TPO antibodies positive (8.3 kU/l). HCG<1 IU/l. Prolactin: 1264 mIU/l. Short SynActhen test: normal response.

Progress: She was transfused 2 units of blood and commenced on tranexamic acid. Levothyroxine was started, initially 50 mg daily, increasing to 100 mg daily after 3 days. An MRI pelvis showed an unremarkable uterus. At thyroid ultrasonography, the parenchyma was atrophic, hypoechoic and heterogeneous consistent with a thyroiditis.

Follow-up: In view of the hyperprolactinaemia, an MRI pituitary scan was ordered. This showed a soft tissue mass 12 x 10 x 14 mm within the sella turcica with strong post contrast enhancement, displacing the optic chiasm thought likely to represent a pituitary macroadenoma. Ophthalmic assessment revealed full visual perimetry and normal acuities. An interval pituitary scan at 5 months, when her TSH was corrected (0.62mU/l), showed complete resolution of the pituitary enlargement.

Discussion: Pituitary hyperplasia manifesting as increased sella turica volume occurs in 25-81% of patients with primary hypothyroidism, due to lack of negative feedback, and correlates with the severity of the thyroid deficiency. It is important to be aware of this condition as the appearance on pituitary scan can mimic a pituitary macroadenoma. Patients may develop visual field defects if the hyperplastic pituitary compresses the optic chiasm. Early recognition is important to avoid unnecessary surgery as the pituitary mass will completely regress with levothyroxine treatment.