Autoimmune hypothyroidism is three times more frequent in female prolactinoma patients compared to healthy women: data from a cross-sectional case-control study.

BACKGROUND: The potent immunomodulatory action of prolactin has been demonstrated in many experimental in vitro studies. In accordance with these data, our retrospective analyses revealed higher prevalence of autoimmune thyroid diseases in prolactinoma patients compared to general population.
PURPOSE: A cross-sectional case-control study was carried out in a single tertiary referral centre. The main aim was to assess the frequency of newly diagnosed autoimmune thyroid diseases in female patients with prolactinomas.
METHODS: The study population consisted of 260 females (154 patients and 106 sex-matched, ethnicity-matched, and age-matched healthy controls) enroled in a prospective manner. Physical exam, thyroid ultrasound, and laboratory testing (measurement of antibodies to thyroglobulin, thyroid peroxidase, TSH-receptor, serum TSH and FT4 levels) were performed in all study participants.
RESULTS: Autoimmune thyroid diseases were diagnosed in 29.9% of the patients and 10.4% of the healthy subjects (p  = 0.0002). Subclinical hypothyroidism was found in 9.7% of the patients versus 2.8% of the controls (p  = 0.044). Autoimmune hyperthyroidism was observed in 1.3% of all patients.
CONCLUSIONS: The prevalence of newly diagnosed autoimmune thyroid diseases, and especially the subclinical hypothyroidism, was significantly higher in our female prolactinoma patients in comparison to age-matched healthy women. Based on our results, we suggest routine screening for autoimmune thyroid diseases (thyroid function, immunology and ultrasound examination) in all female patients with prolactinoma at the time of diagnosis. We also recommend a close follow-up of thyroid function in these women in case of pregnancy and after delivery.