Effect of octreotide acetate on thyrotropin-secreting adenoma: report of two cases and review of the literature.

OBJECTIVE To present two cases with thyrotropin-secreting adenoma and the effectiveness of octreotide acetate treatment on their tumor size as well as on thyroid stimulating hormone (TSH) and thyroid hormone levels. CASE REPORTS The first case presented with tremor, palpitations and sweating as suggestive of hyperthyroidism, but the other one presented with predominantly headache, while the other symptoms such as palpitation and nervousness were less prominent and he also did not have any thyroid enlargement at physical examination. Thyroid hormone levels in both cases were increased. However, TSH levels were not suppressed thus indicating an inappropriate secretion of TSH. Moreover, TSH levels did not change after T3 and TRH administration, which also contributed to the assumption of an inappropriate TSH secretion. One case had no increase in the TSH alpha subunit level, while this was increased in the other one. Both magnetic resonance imaging and somatostatin receptor scintigraphy revealed that there was a microadenoma (the first case; 6 x 7 mm in diameter)and a macroadenoma (the second case; 14 x 18 mm in diameter). Both patients were placed on a therapy with somatostatin analog octreotide (Sandostatin, Sandoz). Octreotide was initially given at a dose of 300 microg daily and then increased gradually up to 600 microg per day. There was some decrease in the levels of TSH and thyroid hormones at first. However, such decreases did not persist with ongoing therapy for 6 months. In addition, there was no change in the tumor size with this therapy at the end. CONCLUSIONS We conclude that the treatment by somatostatin analogue octreotide may not be an effective means of reducing the pituitary tumor size, though it may be used to reduce TSH and thyroid hormones temporarily.