Hyperprolactinaemia associated with increased thyroid volume and autoimmune thyroiditis in patients with prolactinoma.

Objective: The aim of this investigation was to evaluate the effects of hyperprolactinaemia on thyroid function, volume and nodularity in patients with prolactinoma.
Context: Hyperprolactinaemia has been associated with various autoimmune diseases; however, the data on the correlation between the level of prolactin (PRL) and thyroid disorders have not been adequately clarified.
Design: Case-control study.
Patients: Forty-eight subjects with new diagnosis of hyperprolactinaemia (group 1) and 39 subjects undergoing treatment for prolactinoma (group 2) were recruited from our outpatient clinic. Fifty-two healthy subjects were included as a control group (group 3).
Measurements: The serum PRL, thyroid-stimulating hormone (TSH), thyroxine (free T4), thyroidal microsome (anti-TPO) and antithyroglobulin antibodies (TgAb) levels were evaluated, and ultrasonographic thyroid volume was calculated.
Results: The frequencies of positive anti-TPO and TgAb were significantly higher in group 1 than in groups 2 and 3 (P = 0·008). Also, the percentage of patients with thyroid heterogeneity were significantly higher in groups 1 and 2 than in group 3 (P < 0·05). The percentage of patients with thyroid nodules were higher in group 1 than in groups 2 and 3 (p1-2 = 0·03, p1-3 = 0·05 and p2-3 = 0·637). The mean thyroid volume was significantly higher in group 1 (P = 0·001), and a positive correlation was found between thyroid volume and the level of PRL (r = 0·616; P = 0·0001). Prolactin had a significant effect on the total volume according to stepwise multiple linear regression analysis (adjusted R(2) is 0·268; P < 0·0001).
Conclusions: Patients with hyperprolactinaemia have significantly increased thyroid volume, thyroid autoimmunity and nodule prevalence.
(© 2013 John Wiley & Sons Ltd.)