Background and Aims: Thyrotropin-stimulating pituitary adenoma (TSHoma) are a rare entity, occurring in 1 per million people. We performed a systematic review of 535 adult cases summarizing the clinical, biochemical, hormonal and radiological characteristics of TSHoma. Furthermore, we discuss the current guidelines for diagnosis and treatment. Methods A structured research was conducted using Pubmed with the following MeSH terms: “thyrotropin secreting pituitary adenoma” OR “TSHoma” OR “thyrotropinoma”. Results Our analysis included 535 cases originating from 18 case series, 5 cohort studies and 91 case reports. Mean age at diagnosis was 46 years. At presentation 75% had symptoms of hyperthyroidism, 55.5% presented with a goitre and 24.9% had visual field defects. Median TSH at diagnosis was 5.16 (3.20-7.43) mU/L with a mean fT4 of 41.5±15.3 pmol/L. The majority (76.9%) of the TSHoma were macroadenoma. Plurihormonality was seen in 37.4% of the adenoma with a higher incidence in macroadenoma. Surgical resection of the adenoma was performed in 87.7% patients of which 33.5% had residual pituitary adenoma. Postoperative treatment with a somatostatin analogue led to a stable disease in 81.3% of the cases with residual tumour. We noticed a significant correlation between the diameter of the adenoma and residual pituitary adenoma (r=0.490, p<0.001). However, in patients pre-operatively treated with somatostatin analogue this correlation was absent. Conclusion TSHoma are a rare cause of hyperthyroidism and are frequently misdiagnosed. Based on our structured analysis of case series, cohort studies and case reports, we conclude that the majority of TSHoma are macroadenoma being diagnosed in the 5-6th decade of life and presenting with symptoms of hyperthyroidism. Plurihormonalitiy is observed in one third of TSHoma. Treatment consists of neurosurgical resection and SSA in case of surgical failure.

Abnormal thyroid function tests in this euthyroid patient were found to be false due to significant interference of supraphysiological levels of plasma biotin. Laboratory tests applying immunoassays using a biotin-containing reagent should be interpreted with caution in patients on biotin substitution.

A female hemodialysis patient with galactorrhea due to hyperprolactinemia was treated with different dialysis modalities to assess the effect on prolactin levels. A single session of both high-flux hemodialysis and hemodiafiltration resulted in decreased prolactin levels (16,6% and 77,2%, resp.). However, baseline prolactin levels measured immediately before the next dialysis session did not change markedly. After cabergoline treatment was started, prolactin levels normalized and galactorrhea disappeared. Thus, dopaminergic inhibition of prolactin secretion might be reduced in patients with end-stage renal disease. This dopaminergic resistance could be an important mechanism of hyperprolactinemia in hemodialysis patients and its subsequent treatment strategies.