Thyroid autoimmunity in patients with hyperprolactinemia: an observational study

To establish whether there is a relationship between hyperprolactinemia and primary thyroid disorders, focusing on patients with autoimmune features.

The medical records of 100 patients with hyperprolactinemia (HPRL) were retrospectively examined. Records of thyroid ultrasonography (USG), basal serum levels of thyroid stimulating hormone, circulating free thyroxine, free triiodothyronine, antithyroglobulin (anti-Tg), and antithyroperoxidase (anti-TPO) antibodies were analyzed. In 100 control subjects, matched by age and gender with HPRL patients, thyroid USG, thyroid function tests (TFTs), and autoantibody panel were obtained.

The median PRL in patients was 93 ng/mL (range: 37-470). Twenty-five patients (25%) and 22 controls (22%) had positive anti-Tg and/or anti-TPO titers (P = 0.739). The median serum PRL was 98 (37-470) ng/mL in patients with positive thyroid autoantibodies, and 92 (40-470) ng/mL in patients who were negative (P = 0.975). Among the individuals with autoantibody positivity TFTs abnormalities were more frequent in HPRL patients (60%, out of 25 patients, 14 with subclinical hypothyroidism and one with hyperthyroidism) than in controls (9.1%, out of 22 patients, 2 with subclinical hyperthyroidism) (P < 0.001). Twenty-seven patients with HPRL and 31 controls had goiter (27 vs. 31%, P = 0.437). Forty-six patients (46%) and 50 (50%) controls had one or more of the features of thyroid disorder, which were goiter, positive thyroid autoantibody, and thyroid function abnormality (P = 0.888).

HPRL may be associated with more severe thyroid dysfunction in patients with thyroid autoimmunity.