Endocrinological diagnosis and treatment of TSH-secreting pituitary adenomas

Thyrotropin-secreting pituitary adenomas (TSPAs) are very rare pituitary adenomas. In most cases the diagnosis is established by biochemical tests showing syndrome of inappropriate TSH secretion. Otherwise the diagnosis is suspected based on clinical presentation and/or the incidental discovery of a pituitary mass. The clinical presentation of TSPA often overlaps with the presentation of other forms of hyperthyroidism, posing a diagnostic challenge. In particular the presentation of another rare disorder, the resistance to thyroid hormones, is often difficult to distinguish from the presentation of TSPA. The clinical, biochemical, genetic, and imaging characteristics of these two diseases, as well as a stepwise approach to diagnosis, are discussed here. With currently available techniques a definitive diagnosis can be established in the majority of cases. It is crucial to appropriately diagnose and manage TSPAs to avoid unnecessary thyroid ablation and significant enlargement of the pituitary tumor. First-line therapy for TSPA is selective transsphenoidal pituitary surgery. The administration of long-acting somatostatin analogs is an effective second-line medical treatment. The goal of both medical and surgical therapy is to restore an euthyroid state and remove or control the size of the pituitary mass.