Palpitations and the Pituitary the Case of Assay Interference


S G Wijetilleka, S Qureshi, R Kaushal


We would like to present a pituitary incidentoloma which was initially thought to be a TSH-oma. We reviewed a 53 year old Indian male with no past medical history who presented to his GP with palpitations in December 2015. He reported weight loss and six loose stools per day. He attended endocrine clinic in Jan 2016.


  Post-clinic bloods revealed TSH of 2.13, T4 of 21.3, T3 5.4, TSH receptor antibody of 0.5, FBC and U&E were normal.

  USS thyroid revealed a small nodule in the left thyroid (3.7mm), otherwise normal left and right lobes. The patient was sent for an NM thyroid scan which was a normal study with no evidence of a toxic adenoma.

  He was started on carbimazole 20mg od and propranolol 10mg tds prn.


He returned to endocrine clinic in April 2016 and was clinically euthyroid TSH was 4.89, T4 was 27.5 and T3 was 5.7. His FBC, UE and LFTs were normal. 9am cortisol was 143, FSH 7.4, LH 4.5, PRL 114, IGF1 34,testosterone 8.7 and his SHBG was 31.6 (FAI 27.5%).


We performed a short synacthen test which was within normal limits and invited this gentleman for a pituitary MRI in May 2016.


A pituitary mass was seen on MRI in May 2016; a 4mm cyst was visualised behind the infundibulum.


He was discussed in the pituitary MDT at Imperial College in July 2016. He was asked to attend Imperial for further bloods, namely thyroid function tests with different assays. Conditional to this he was invited for a TRH test and a T3 stimulation test and an alphasubunit radio was sent.


Repeating bloods at Imperial College led to his TSH, T4 and T3 being within normal limits. As our patient was clinically euthyroid now and remains completely asymptomatic on further clinical review.