Endocrine Abstracts

A 69-year-old female presented in 2002 with symptoms of hyperthyroidism. Thyroid function tests confirmed thyrotoxicosis with elevated fT₄ and fT₃ but with an elevated TSH (TSH 5.8 mU/l, fT₄ 31.7 pmol/l, fT₃ 8.1 pmol/l). Pituitary function tests other than the TSH were normal. Pituitary MRI showed a mass in the left half of the pituitary fossa, displacing the stalk to the right with no suprasellar extension. A T₃ suppression test was normal excluding thyroid hormone resistance. An octrotide scan showed a well-defined lesion in the pituitary fossa that demonstrated intense octreotide uptake. A TRH test dose produced a flat TSH response (t=0 min TSH 2.1, t=60 min TSH 1.9 mU/l) which was highly suggestive of a pituitary TSH-secreting adenoma. The patient declined surgery. Therefore a novel test octrotide infusion was administered. After 24-hours of octreotide, the TSH fell from a baseline of 3.5 mU/l (with fT₄ 20.3 pmol/l) to 1.4 (fT₄ 17.4). Subsequently she was commenced and maintained on octreotide LAR 20 mg subcutaneous injections monthly. Initial MRI follow-up scans showed no significant change. However, a reduction in size of the pituitary tumour was observed on an MRI scan in September 2004 Thyroid function tests have remained within the normal ranges on octreotide therapy (August 2005: TSH 2.48 mU/l, fT₄ 16.2 pmol/l, fT₃ 5.3 pmol/l). In conclusion, this case illustrates that TSH-secreting adenomas may be successfully treated medically with octreotide therapy leading to normalisation of thyroid function tests and tumour shrinkage. Thus octreotide could obviate the need for surgical intervention in some cases.