Thyroid Autoimmunity and Subclinical Hypothyroidism in Prolactinoma: A Case Control Study

This study was aimed at determining the frequency of thyroid autoimmunity and subclinical hypothyroidism in patients with hyperprolactinemia due to prolactinoma compared to well-matched healthy controls.

This was a cross-sectional study wherein 78 treatment naïve prolactinoma patients and ninety-two healthy control subjects were recruited. Serum prolactin (PRL), thyroid-stimulating hormone (TSH), total thyroxine (T4), circulating anti-thyroid peroxidase (anti-TPO), and anti-thyroglobulin (anti-Tg) antibody levels were measured in all study subjects. Progression of the antibody-positive population to subclinical hypothyroidism was determined.

The median PRL level among patients was 166 ng/ml (IQR 85-467) compared to 11.4 ng/ml (IQR 8.5-15.9) in controls (P < 0.001). There was no significant difference in levels of T4 (P = 0.83) and TSH (P = 0.82) between the cases and controls. Overall, 25% of patients had the presence of anti-thyroid antibodies as compared to 20% of controls (P = 0.56). SCH was more common in antibody-positive hyperprolactinemia subjects compared with antibody-positive controls.

We did not find an increased prevalence of thyroid autoimmunity among untreated prolactinoma patients compared to healthy controls. At the same time, subclinical hypothyroidism was more common in thyroid antibody-positive patients with hyperprolactinemia than positive controls.