National incidence and prevalence of TSH-secreting pituitary adenomas in Sweden

TSH-secreting pituitary adenomas (TSHomas) are rare. Epidemiological data are scant and there are no reports on national incidence.The objective of the study was to estimate the national Swedish incidence and prevalence of TSHomas.This was an observational study.The study was conducted at tertiary referral centers.The Swedish Pituitary Registry and World Health Organization International Statistical Classification of Diseases and Related Health Problems coding at all university hospitals were used to identify patients diagnosed with TSHomas 1990-2010. The identified patients' medical records were studied until the latest follow-up [median 5.0 years (range1-20 years)].Incidence, prevalence, demographics, tumor characteristics, treatment outcome, and thyroid hormone level at diagnosis were measured.The age-standardized national incidence of 28 TSHoma patients was 0.15 per 1 million inhabitants per year, with an increasing incidence over time (0.05 per 1 million per year in 1990-1994 to 0.26 per 1 million per year in 2005-2009). The national prevalence in 2010 was 2.8 per 1 million inhabitants, in which 0.85 per 1 million had active disease. Most patients (n = 22) underwent pituitary surgery, 5 had radiotherapy, and 6 had somatostatin analogues. Eighteen patients were considered cured at the latest follow-up; 25% remained uncontrolled. Subjects treated for putative primary hyperthyroidism prior to diagnosis had TSH levels more than double those with intact thyroid at diagnosis (P = .013). The median time to diagnosis was longer for women than men (4 vs1 year, P = .026). More women than men were treated surgically (94.1% vs 54.5%, P = .022).This is the first estimate of a national incidence of TSHoma. Additional epidemiological studies are needed to compare these results with other geographical areas. This study suggests an increased incidence of TSHomas, in agreement with reports on other pituitary adenomas.