Medical management of TSH secreting Pituitary Tumours — ASN Events

Medical management of TSH secreting Pituitary Tumours (#361)

Geetha Theverkalam 1 , Jeffrey Zajac 1
  1. Endocrinology, Austin Hospital, Melbourne, Vic, Australia

Thyrotropin secreting tumours are a rare cause of secondary hyperthyroidism.Approximately 1% of functioning pituitary tumours are TSHomas.(1,4).the pathophysiology is that of autonomous secretion of TSH and hence they do not respond to TRH or thyroid hormone feedback. Around 25% may secrete other pituitary hormones. Ultrasensitive TSH assays and improvements in pituitary imaging help in early diagnosis.(4) First described in 1960 the management of these tumours has evolved considerably to include surgery, radiotherapy and medical management. Most patients are managed with multiple modalities of treatment and we are presenting a case in which we have achieved biochemical and clinically euthyroid status with medical management alone for ten years.

An 80-year-old woman was referred in 2003 following investigations for multinodular goitre as she was noted to have inappropriate secretion of TSH with Free T4 28; T3 6.5 and TSH 4.5.Other than AF no symptoms of thyrotoxicosis and she was clinically euthyroid with a small palpable goitre. Past medical history included, hypertension, osteoarthritis with bilateral TKR and bipolar disorder. Investigations include an ultrasound which revealed a multinodular goitre and thyroid uptake scan showed normal uptake of 2.8% with no functioning nodules .MRI Pituitary showed a 10x 10 mm macroadenoma on the L aspect of pituitary with no involvement of the optic chiasm. Endocrine testing showed normal cortisol , prolactin levels,LH and FSH were elevated .An alpha subunit level was elevated at 1.86f IU /L and TSH receptor antibodies were negative. As she was reluctant to undergo neurosurgery, medical management with close monitoring of the pituitary tumour with regular imaging and visual field testing was chosen.For 7 years she was treated with Carbimazole in varying doses 5-20 mg to treat the effects of peripheral hormones. Initially there was a response with lower levels of thyroid hormone but she had increasing levels of TSH with a zenith in October 2010 of 67 .This was accompanied by increasing size of the adenoma to 15x16 mm with suprasellar extension. Her visual fields though remained intact .She was then commenced on Octreotide LAR with rapid reduction in TSH and a borderline reduction in size of the tumour .She remains clinically well.