An increased prevalence of thyroid echographic and autoimmune changes in hyperprolactinemic women on therapy with dopaminergic drugs

: Prolactin (PRL) possesses mitogenic and immunomodulatory properties. We evaluated the prevalence of ultrasonographic thyroid alterations and thyroid autoimmunity in hyperprolactinaemic (HPRL) women and correlated these with PRL levels. Furthermore, we studied the PRL binding in human benign nodular thyroid tissues. 133 HPRL patients (16-63 years) and 103 healthy female controls (16-63 years) with no known history of thyroid disease were studied. Blood samples were collected for PRL, FT3, FT4, TSH, thyroid peroxidase auto-antibodies (TPO Ab) and thyroglobulin auto-antibodies (Tg Ab) assays. All subjects underwent thyroid ultrasonography. PRL binding to thyroid membranes was determined by in-vitro radioreceptor assay in 5 human benign nodular thyroid fragments obtained from female patients. No difference in TSH levels was found, while FT3 (4.5 +/- 0.1 pmol/L) and FT4 (16.2 +/- 0.4 pmol/L) levels were significantly higher in controls than in HPRL (FT3: 3.8 +/- 0.1 pmol/L, p = 0.01, FT4: 15.4 +/- 0.2 pmol/L, p = 0.04). The prevalence of thyroid ultrasonographic alterations (simple goitre, uni-multinodular goitre, chronic thyroiditis) was significantly higher in HPRL (30.8%) than in controls (15.5%, p = 0.01) but did not correlate with mean initial and actual PRL levels or duration of the disease. The prevalence of autoantibodies was significantly higher in HPRL (29.6%) than in controls (14.3%, p = 0.04) but did not correlate with PRL levels. Very low specific PRL binding to thyroid membranes was detected. The high prevalence of thyroid ultrasonographic alterations and autoimmunity in HPRL suggests a possible role of PRL in the development of thyroid diseases. Clinical and instrumental thyroid screening may therefore be advisable in these patients.