Systematic review of the association between thyroid disorders and hyperprolactinemia

Introduction Thyroid disease (TD), particularly hypothyroidism, is an important etiology of hyperprolactinemia (HPRL). We conducted a systematic review of the clinical characteristics, management, and outcomes of adults (> 18 years) with this clinical association. Materials and methods We searched PUBMED, SCOPUS, and EMBASE to find eligible articles published in English from any date till 15th December 2022. Results The final systematic review included 804 patients from 47 articles, of which the majority (85.9%) were females. Menstrual irregularity was the most prominent symptom of HPRL (74.3%). Subclinical hypothyroidism (57.1%) was the most reported TD. Individual patient data were available for 62 patients from 35 studies. The median age was 32 (25-42) years, TSH was 110.25 (50-345.4) mU/L, and PRL level was 60 (37.6-91) ng/ml. On treating TD, 38 (70.4%) patients had complete resolution and 10 (18.5%) had an improvement in HPRL. Of 38 patients with pituitary imaging, 26 (68.4%) showed pituitary enlargement, and 13 (34.2%) showed a suprasellar extension. 13 (76.5%) patients had complete resolution and 3 (17.6%) had an improvement in pituitary enlargement on TD treatment. A positive correlation was observed between higher serum TSH levels and higher serum prolactin levels. Patients with pituitary enlargement on imaging had a higher TSH level compared to those without any pituitary enlargement (Median of 263 (61-602) vs. 50 (24.3-128) mU/L; p-value = 0.01). Conclusion Thyroid hormone replacement can lead to resolution of HPRL and pituitary enlargement in the majority of patients with HPRL due to overt or subclinical hypothyroidism without the need for dopamine agonist treatment.