Patients with thyrotropin-secreting pituitary adenomas may present with mass effect, hypopituitarism, and/or hyperthyroidism. The spectrum of pathologic and clinical features of patients whose tumors demonstrate β-thyrotropin immunoreactivity (β-TSH IR) has not been characterized. To characterize the phenotype of patients with pituitary adenomas with positive β-TSH IR, we conducted a retrospective analysis of patient records of all adult patients (n = 1,223) undergoing pituitary surgery in our institution over one decade (1999-2009). The search identified 166 adults with tumors which had β-TSH IR. These patients were individually matched to 166 patients whose tumors revealed no β-TSH IR. Clinical, pathological, imaging and biochemical data were extracted. 332 patients, aged 51.4 ± 15.1 years [150 women (45 %) and 182 men (55 %)], with pituitary adenomas (mean tumor diameter ± SD: 22.7 ± 9.0 mm) were studied. The degree of β-TSH IR was associated with the presence of central hyperthyroidism (p < 0.0001) or goiter (p = 0.0217). Patients whose tumors expressed more extensive β-TSH IR were less likely to develop pituitary apoplexy than those without β-TSH IR (p = 0.0428). In addition, the degree of β-TSH IR correlated with the presence of immunoreactivity for β-FSH (p < 0.0001), β-LH (p < 0.0001), alpha subunit (p < 0.0001), and GH (p = 0.0036).
Conclusions: Pituitary adenomas expressing β-TSH IR were more likely to demonstrate immunoreactivity for β-FSH, β-LH, GH or alpha subunit. Patients with such tumors were more likely to exhibit hyperthyroidism and goiter, but less likely to develop pituitary apoplexy than patients without β-TSH IR. These findings suggest that β-TSH IR is associated with specific phenotypic features in patients with pituitary adenomas.