Ectopic pituitary adenoma of the TSH-secreting sphenoidal sinus with excellent response to somatostatin analogs. Theory of the embryogenesis and literature review from a clinical case.

Ectopic thyrotropin-secreting pituitary adenomas are rare, with only 10 published cases. We report the case of a 52-year-old woman who was referred for primary hypothyroidism, who showed clinical signs of hyperthyroidism and had been under treatment with levothyroxine. Her exams revealed high levels of thyroid stimulating hormone (TSH), at odds with free thyroxin (FT4) and raised triiodothyronine (T3), which remained elevated after medication suspension, suggesting possible central hyperthyroidism. Sellar MRI showed normal pituitary gland, with a mass in the sphenoid sinus of 24 mm. A possible ectopic TSH secreting pituitary tumor of sphenoid sinus was hypothesized. After a intramuscularly (IM) single dose of a sustained-relase of a somatostatin analog (octreotide) 20 mg, plasma levels of thyroid hormones were normalized and a significant tumor reduction was demonstrated in MRI control at 7-weeks' follow-up. The tumor was removed by transsphenoidal endoscopy, and the biopsy confirmed an adenoma with positive immunostaining for TSH and GH. Hyperthyroidism recurrence was observed in hormonal controls 4 weeks after surgery. Treatment with sustained-release octreotide was reinitiated, every 60-days for two years, with normalization of the thyroid hormone profile, but with a residual lesion with the appearance of a tumor in the MRI. A second tumor resection was performed, achieving sustained hormonal cure and no residual tumor lesion at 2-years' follow-up. To our knowledge, this is the first report of an ectopic thyrotropin-secreting pituitary adenoma of the sphenoid sinus. Clinical and laboratory aspects relevant to this entity are reviewed, emphasizing the usefulness of octreotide in the management of the reported case.