Endocrine Abstracts

Objective: To study the clinical, diagnostic and morphological characteristics and treatment outcomes of TSH-secreting pituitary tumors.

Patients and methods: The study included 21 patients with pituitary adenoma and a normal or elevated TSH level and elevated fT₄ and fT₃ levels who were operated on at the Neurosurgical Institute in the period between 2002 and 2015. Before surgery, in the early postoperative period, and 6 months after surgery, the patients were tested for levels of TSH, fT₄, fT₃, prolactin, cortisol, LH, FSH, estradiol/testosterone, IGF-1. The thyroid status was evaluated using the following reference values: TSH, 0.4–4.0 mIU/l; fT₄, 11.5–22.7 pmol/l; fT₃, 3.5–6.5 pmol/l. An immunohistochemical study of material was performed with antibodies to TSH, PRL, GH, ACTH, LH, FSH, and Ki-67 (MiB-1 clone); in 13 cases, we used tests with antibodies to somatostatin receptors type 2 and 5 and to D2 subtype dopamine receptors.

Results: TSH-secreting tumors were detected in patients aged from 15 to 67 years (median 39 years), males (48%) and females (52%). Before admission to the Neurosurgical Institute, 11 (52%) patients were erroneously diagnosed with primary hyperthyroidism; seven of these patients underwent surgery on the thyroid gland and/or received thyrostatics (four cases). Hyperthyroidism symptoms were observed in 16 (76%) patients. The level of TSH was 2.47–38.4 mIU/l (median, 6.56); fT₄, 22.8–54.8 nmol/l (median, 36); fT₃, 4.24–12.9 pmol/l (median, 9.66). Tumors had the sellar localization in 4 (19%) cases and the parasellar localization in 17 (91%) cases. Total tumor resection was performed in 7 (33%) patients. All these tumors had the sellar and suprasellar localization. No total resection was performed in patients with infiltrative growth of adenoma (invading the skull base structures). An immunohistochemically study of tumor resection specimens detected TSH expression in 21 (100%) cases; 18 (86%) tumors were plurihormonal and secreted TSH and GH and/or PRL. Of 13 tumors, expression of the type 2 dopamine receptor was detected in 9 (69%) cases; expression of somatostatin receptors type 5 and type 2 was found in 6 (46%) and 2 (15%) cases, respectively.

Conclusion: The criterion for total tumor resection was a postoperative TSH level decrease to 0.1 mIU/l or less. Total resection was performed in 33% of patients with sellar and suprasellar tumors only. In most cases, tumors were plurihormonal secreting TSH and GH and/or PRL.