The higher incidence of autoimmune thyroid disease in prolactinomas than in somatotrophinomas Sema Ciftci Dogansen a, ⁎, Ozlem Soyluk Selcukbiricik a , Betul Ekiz Bilir b , Sema Yarman a a Istanbul University, Istanbul Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism, Istanbul, Turkey b Trakya University, Trakya Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism, Edirne, Turkey abstract article info Article history: Received 29 October 2015 Received in revised form 3 February 2016 Accepted 8 April 2016 Available online 11 April 2016 Objective: Many studies have shown that prolactin (PRL) plays an important role in autoimmune diseases. The aim of this study was to compare the current frequency of autoimmune thyroid disease (ATD) in prolactinomas with another type of functional pituitary adenoma (FPA), somatotrophinoma. Another aim of the study was to evaluate possible factors related to thyroid autoimmunity and the process of ATD in FPAs. Methods: We retrospectively evaluated the presence of thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) and thyroid morphologic findings in our patients with FPA (78 with acromegaly and 83 with prolactinoma). The relationship of autoantibody positivity with baseline PRL levels, activity of acromegaly, and treatment of dopamine agonists (DA) and hypogonadism was also assessed. Patients with ATD and hypothyroid- ism due to autoimmune thyroiditis were also evaluated. Results: ATD (Hashimoto's thyroiditis) was detected more frequently in patients with prolactinoma than in pa- tients with acromegaly (33% and 17%, respectively; p = 0.01). Thyroid autoantibody positivity was found more frequently in females in the whole group (p = 0.02) and in the acromegaly group (p = 0.008). There was no difference according to sex among the patients with prolactinoma (p = 0.800). ATD was found not to be related with baseline PRL levels, treatment of DA, and presence of hypogonadism (p = 0.232, p = 0.435, p = 0.464, respectively) in the prolactinoma group, and activity of acromegaly, presence of hypogonadism in the acromegaly group (p = 0.753, p = 0.654, respectively). Autoimmune hypothyroidism was more frequent in the prolactinoma group than in the acromegaly group among patients with thyroid autoantibody positivity (p = 0.004). Conclusion: Thyroid autoantibodies should be evaluated both at the time of diagnosis and during the course of treatment in patients with prolactinoma, and thyroid function tests should be closely monitored in patients with autoantibody positivity. © 2016 Elsevier Ltd. All rights reserved. Keywords: Autoimmune thyroid disease Hashimoto's thyroiditis Prolactinoma Hyperprolactinemia Somatotrophinoma Acromegaly 1. Introduction Prolactin (PRL) is secreted from lactotroph cells of the anterior pitu- itary gland and also from some extrapituitary tissues, such as immune cells, neurons, prostate, decidua, breast, and skin [1]. PRL is also struc- turally similar to members of hematopoietic cytokine family, and PRL plays a proinflammatory role by binding to PRL receptors (PRL-R) locat- ed on T lymphocytes, B-lymphocytes, and macrophages [2]. PRL causes immunoglobulin and antibody production by stimulating immune cells via its receptors [3]. Many studies have shown that PRL plays an impor- tant role in autoimmune diseases such as systemic lupus erythemato- sus, rheumatoid arthritis, primary Sjögren's syndrome, type 1 diabetes mellitus, systemic sclerosis, Addison's disease, pernicious anemia, pri- mary biliary cirrhosis, celiac disease, myasthenia gravis, and autoim- mune thyroid disease (ATD) [4]. Pelkonen et al. [5] were the first to review the relationship between hyperprolactinemia and ATD. Later, Ferrari et al. [6] found that the prevalence of thyroid autoantibody positivity was significantly higher in patients with prolactinoma than controls. Most studies since that time have shown that the incidence of ATD is increased in hyperprolactinemia [7–11]. Acromegaly is frequently associated with the presence of goiter, espe- cially nodular goiter, but the prevalence of ATD is reported low [12–15]. However, one study reported that the frequency of ATD was higher in patients with acromegaly compared with the general population [16]. In the literature, one study has compared the presence of thyroid au- toantibodies between prolactinomas and somatotrophinomas [10]. Growth Hormone & IGF Research 29 (2016) 45–49 Abbreviations: AA, active acromegaly; ATD, autoimmune thyroid disease; CA, cured acromegaly; DA, dopamine agonist; ECLIA, electrochemiluminescent immunoassay; FPA, functional pituitary adenoma; GH, growth hormone; IGF-1, insulin growth factor-1; LT4, levothyroxine; PRL, prolactin; PRL-R, PRL receptors; SD, standard deviation; Th, T helper; TgAb, thyroglobulin antibody; TPOAb, thyroid peroxidase antibody; USG, ultrasonogra- phy; WCA, well-controlled acromegaly. ⁎ Corresponding author at: Istanbul University, Istanbul Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism, Capa, 34090 Istanbul, Turkey. E-mail address: sdogansen@gmail.com (S.C. Dogansen). http://dx.doi.org/10.1016/j.ghir.2016.04.004 1096-6374/© 2016 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Growth Hormone & IGF Research journal homepage: www.elsevier.com/locate/ghir