Endocrine Abstracts

Background: TSH-secreting tumors appears as extremely rare cause of hyperthyroidism. Major clinical feature is preserved TSH level in subjects with apparent thyrotoxicosis. Misdiagnosis of primary thyroid hyper function led to mistreatment with anti-thyroid agents. This worsens disease course and outcome. Neurosurgery success rate is limited by large tumor size and extrasellular expansion. Somatostatin plays key role in regulation of TSH secretion. Tumors in most cases expresses receptors for somatostatin therefore SRL are potent option in TSH-oma treatment.

Aim: Of the study was to determine SRL efficacy in patients before neurosurgical treatment of TSH-oma. Secondary aim was to verify long-period outcome of SRL in cases of neurosurgery failure.

Material: Comprise of 9 patients with secondary thyrotoxicosis, 6 women and 3 men, aged 35 to 69 yrs (mean 49) presenting with pituitary macroadenoma (18 to 45 mm). Before diagnosis was established, 5 out of 9 received antithyroid medication, and in 1 case strumectomia was performed.

Intervention: Somatostatin analogue octreotide long-acting repeatable (LAR) administration 3 months prior to the surgery.

Results: Initially, all patients had abnormal fT4 and alfa-SU levels (mean 38.8 pmol/l SD 11.6 and 6.1 ng/ml SD 6.4, respectively) as well as lack of TSH increase after TRH stimuli (mean rise 15% from basal value, SD 52). 3 months of SRL treatment led to marked TSH and alfa-SU levels decrease (to 1.2 mU/l SD 1.1 and 0.8 ng/ml SD 0.6, resp.), normalization of thyroid hormones (fT4 mean 15.7 pmol/l SD 5.0) and clinical improvement. Patients in euthyroid state were referred to neurosurgery unit. Tanssphenoideal adenomectomy was successful in 8 out of 9, and in this group TRH stimuli performed 3 months after surgery provokes significant TSH response (mean rise 210% SD 310). In one case after unsuccessful surgery euthyroid state is achieved during SRL treatment for 2 years, without noticeable adverse events.

Conclusions: Somatostatin analogue treatment is efficient in TSH-secreting tumors in inhibition of TSH secretion, thyroid hormone normalization, visual field improvement, thyroid volume decrease and neurosurgery success rate. Post-surgery TSH increase during TRH test indicates restored pituitary-thyroid axis. In cases of surgery failure prolonged SRL may be efficient option.