Endocrine Abstracts

We present a 43 year old gentleman of Bangladeshi origin, who was referred to us by his GP with increased sweating, palpitations and anxiety for the last few years and abnormal thyroid functions. He complained of headaches, tremors, weight loss, increased appetite and sleep disturbances in addition to the above symptoms. He had no other significant past, family or social history. On examination in the clinic, he was found to have a raised blood pressure. He had phenotypical features of acromegaly such as coarse orbital ridges, prognathism with dental malocclusion, broad nose and large sweaty hands with tremors. He did not have a visible goitre. His initial blood tests showed a high free T3 (27.1 pmol/l), a high free T4 (55.0 pmol/l) with a raised TSH (5.93 mIU/l). His GH (15.1 mg/l), and IGF-1 (402 ng/ml) were also raised. To distinguish from Thyroid hormone resistance, his α-subunit, and SHBG were checked, and both of these were raised at 18.7 IU/l and 129 nmol/l respectively. He underwent an OGTT which failed to suppress his Growth hormone. His Pituitary MRI revealed a 4 cm macroadenoma with displacement of optic chiasm and carotid arteries. He was referred to the local tertiary pituitary MDT and commencement of Lanreotide and surgery was recommended. The patient was reluctant for surgery at this point, he was hence started on carbimazole, propranolol and Lanreotide 120 mg SC every four weeks. Five months into the above intervention, a marked reduction in the size of the pituitary macroadenoma was noted on a repeat MRI. There was a significant improvement in his TFTs (fT3 pmol/l, fT4 29 pmol/l, TSH 1.56 mIU/l), SHBG (49.6 nmol/l). His IGF1 though showed only marginal improvement (352 ng/ml). He was rediscussed in the Pituitary MDT and continuation of Lanreotide and a repeat surgical offer was recommended. A TSH-GH co-secreting pituitary macroadenoma is a rare tumor. The prevalence of a TSHoma is estimated to be less than 1 per million general population. Of these <30% of are plurihormonal, with GH being the most commonly co-secreted hormone. It is essential to correctly identify and address the co-secretion to avoid incomplete management of such plurihormonal adenomas.

Discussion: • The use of Carbimazole is controversial in a TSHoma.

• Awareness of the possibility of co-secreting pituitary tumors is essential to identify such tumours.

• Surgery remains mainstay of treatment, somatostatin analogs can be used in the interim.