Successful Multimodal Treatment of a TSH-Secreting Pituitary Adenoma (TSH-oma)

Background: TSH-omas are rare tumors accounting for 0.5-2% of all pituitary adenomas. Due to their indolent nature, most TSH-omas are diagnosed at the stage of invasive macroadenomas. Over the past several decades, the management of TSH-omas has evolved substantially. While surgery remains first-line therapy, somatostatin analogs have emerged as important therapeutic agents as a result of their effectiveness in normalizing thyroid hormone levels in ~95% of patients with severe hyperthyroidism and reducing TSH-oma size in ~50% of patients. Clinical Case: A 52-year-old woman with a history of multinodular goiter was incidentally found to have a 2.2 x 1.8 x 2.1 cm pituitary macroadenoma with suprasellar extension, mass effect on the optic chiasm, and left cavernous sinus involvement when she presented with chest pain, palpitations, headache, and left-sided numbness and weakness. Laboratory results showed high FT4/T4/T3 with inappropriately high TSH, elevated α-subunit, and low cortisol with low-normal ACTH highly suggestive of TSH-oma with concurrent secondary adrenal insufficiency. An ophthalmology exam revealed a left superior temporal defect. The patient was treated with atenolol, prednisone, and octreotide two weeks before surgery with symptomatic improvement and near-normalization of FT4. Following an uncomplicated transsphenoidal resection, FT4 normalized within one week. At her one-month follow-up, both TSH and FT4 were normal, and her secondary adrenal insufficiency had resolved. Her visual field defect also recovered. Laboratory Results: TSH 5.35 (normal range 0.40-4.60 μU/mL), FT4 3.0 (0.8-1.7 ng/dL), T4 18.1 (5.0-12.0 μg/dL), T3 235 (80-200 ng/dL), ACTH 10 (6-50 pg/mL), cortisol 4.5 (5.0-25.0 μg/dL), α-subunit 8.0 (0.1-1.5 ng/mL); after 2 weeks on SQ octreotide 50mg q12h: TSH 1.93 (0.30-4.20 μU/mL), FT4 1.7 (0.6-1.5 ng/dL); 1 month post-op: TSH 1.53 (0.30-4.20 μU/mL), FT4 0.8 (0.6-1.5 ng/dL), ACTH 12 (7.2-63 pg/mL), cortisol 6.9 (4.0-20.0 μg/dL) Conclusion: Since the first reported case of TSH-oma in 1960, the diagnostic and therapeutic management of these rare pituitary adenomas have evolved due to the emergence of ultrasensitive TSH assays, advanced imaging and surgical techniques, and somatostatin analogs. However, to this day, most TSH-omas are still diagnosed at the stage of invasive macroadenomas, when successful surgical resection becomes more difficult. Hence, up to two-thirds of patients may require adjuvant therapy with medication or radiation. As evidenced in our patient, who achieved a near-euthyroid state within just two weeks of starting low dose octreotide, somatostatin analogs are highly effective in controlling hyperthyroidism and have solidified their place in the therapeutic management of TSH-omas. This case highlights the success of a multimodal approach to the treatment of TSH-omas.