High prevalence of autoimmune thyroid diseases in patients with prolactinomas: A cross-sectional retrospective study in a single tertiary referral centre

Background Prolactin has been shown to exert potent immunomodulatory activities. Design Retrospective cross-sectional study examining the prevalence of autoimmune thyroid diseases (AITD) in patients with prolactinomas. The medical files of 462 patients (367 women and 95 men) followed up at a single tertiary referral centre were analyzed. Results The prevalence of AITD among prolactinoma patients was estimated at 21.0% (23.2% in females and 12.6% in males). In 51.5% of the patients, diagnosis of prolactinoma preceded the development of AITD; in 37.2%, both diseases were simultaneously diagnosed and 11.3% of patients were diagnosed first with AITD. Hyperthyroidism was observed in 1.24% of the investigated subjects. Primary hypothyroidism was detected in 15.6% of all patients (16.4% in women; 10.7% in men) with a mean incidence of 24 cases/1000/year. Conclusions Our results demonstrate the high frequency of AITD in patients with prolactinomas. The prevalence rate of hyperthyroidism is comparable with the literature data from community-based studies. In contrast, the prevalence of the spontaneous hypothyroidism due to autoimmune thyroiditis is significantly higher in female and male subgroups of patients with prolactinomas in comparison with the general population. A possible role of supraphysiologically increased prolactin levels in the pathogenesis and the clinical course of AITD in patients with prolactinomas can be suggested. Based on these findings we recommend routine screening for AITD with simple thyroid tests (TSH, TPO-Abs and ultrasound examination) in all patients diagnosed with prolactinoma.