TSH-secreting pituitary adenomas (TSHomas) are rare. Previously, the reported prevalence was one case per million populations although this is probably an underestimate. A recently published study reported a prevalence of TSHomas in Sweden of 2.8/million inhabitants.
Methods/design: Observational study conducted in four tertiary referral centres in Ireland. We retrospectively collected data on the prevalence, demographics, hormonal profile, tumour characteristics, and treatment outcomes for patients with TSHomas.
Results: 21 patients (eight males) were diagnosed with TSHoma between 1968 and 2014. Mean age at diagnosis was 46 years. The prevalence of TSHomas in Ireland (Republic of Ireland and Northern Ireland) is 3.3/million inhabitants. This may be an underestimate as other centres may have TSHomas that were not included. At diagnosis, the median free thyroxine was 49.9% (IQR 50.3%) above the upper reference range. Eleven patients (52%) had TSH within normal range at diagnosis. 5/21 (23.8%) patients co-secreted GH and 4/21 (19%) patients had elevated prolactin. The median adenoma size was 13.5 mm (IQR 18.7) and 12/21 patients had a macroadenoma.15/21 patients were treated with surgery (two required craniectomy) as a primary therapy, 6/21 were treated with a somatostatin receptor ligand (SRL), five as a primary therapy. Somatostatin analogues normalised thyroid function in 4/5 patients. 8/21 patients underwent radiotherapy for either persistent active disease or tumour growth. 4/21 had hormonally active disease at the last follow up; three of these were treated with transsphenoidal surgery and radiotherapy and one with SRL. 11/21 (52%) had other pituitary hormones deficiencies at the most recent follow up.
Conclusion: The prevalence of TSHoma in Ireland exceeds the previously cited estimate of one case per million. Multimodal treatment is often required to normalise thyroid function and prevent tumour growth.