title: Mechanisms in endocrinology: thyroid and polycystic ovary syndrome.
abstract: Thyroid disorders, especially Hashimoto's thyroiditis (HT), and polycystic ovary syndrome (PCOS) are closely associated, based on a number of studies showing a significantly higher prevalence of HT in women with PCOS than in controls. However, the mechanisms of this association are not as clear. Certainly, genetic susceptibility contributes an important part to the development of HT and PCOS. However, a common genetic background has not yet been established. Polymorphisms of the PCOS-related gene for fibrillin 3 (FBN3) could be involved in the pathogenesis of HT and PCOS. Fibrillins influence the activity of transforming growth factor beta (TGFβ). Multifunctional TGFβ is also a key regulator of immune tolerance by stimulating regulatory T cells (Tregs), which are known to inhibit excessive immune response. With lower TGFβ and Treg levels, the autoimmune processes, well known in HT and assumed in PCOS, might develop. In fact, lower levels of TGFβ1 were found in HT as well as in PCOS women carrying allele 8 of D19S884 in the FBN3 gene. Additionally, vitamin D deficiency was shown to decrease Tregs. Finally, high estrogen-to-progesterone ratio owing to anovulatory cycles in PCOS women could enhance the immune response. Harmful metabolic and reproductive effects were shown to be more pronounced in women with HT and PCOS when compared with women with HT alone or with controls. In conclusion, HT and PCOS are associated not only with respect to their prevalence, but also with regard to etiology and clinical consequences. However, a possible crosstalk of this association is yet to be elucidated.
authors.affiliation: Department of Nuclear MedicineUniversity Medical Centre Ljubljana, Zaloška 7, 1525 Ljubljana, SloveniaFaculty of MedicineUniversity of Ljubljana, Vrazov trg 2, 1104 Ljubljana, SloveniaDivision of Endocrinology and MetabolismDepartment of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria Department of Nuclear MedicineUniversity Medical Centre Ljubljana, Zaloška 7, 1525 Ljubljana, SloveniaFaculty of MedicineUniversity of Ljubljana, Vrazov trg 2, 1104 Ljubljana, SloveniaDivision of Endocrinology and MetabolismDepartment of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria.
authors.forename: Simona
authors.initials: S
authors.lastname: Gaberšček
authors.affiliation: Department of Nuclear MedicineUniversity Medical Centre Ljubljana, Zaloška 7, 1525 Ljubljana, SloveniaFaculty of MedicineUniversity of Ljubljana, Vrazov trg 2, 1104 Ljubljana, SloveniaDivision of Endocrinology and MetabolismDepartment of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria.
authors.forename: Katja
authors.initials: K
authors.lastname: Zaletel
authors.affiliation: Department of Nuclear MedicineUniversity Medical Centre Ljubljana, Zaloška 7, 1525 Ljubljana, SloveniaFaculty of MedicineUniversity of Ljubljana, Vrazov trg 2, 1104 Ljubljana, SloveniaDivision of Endocrinology and MetabolismDepartment of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria.
authors.forename: Verena
authors.initials: V
authors.lastname: Schwetz
authors.affiliation: Department of Nuclear MedicineUniversity Medical Centre Ljubljana, Zaloška 7, 1525 Ljubljana, SloveniaFaculty of MedicineUniversity of Ljubljana, Vrazov trg 2, 1104 Ljubljana, SloveniaDivision of Endocrinology and MetabolismDepartment of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pieber
authors.affiliation: Department of Nuclear MedicineUniversity Medical Centre Ljubljana, Zaloška 7, 1525 Ljubljana, SloveniaFaculty of MedicineUniversity of Ljubljana, Vrazov trg 2, 1104 Ljubljana, SloveniaDivision of Endocrinology and MetabolismDepartment of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria barbara.obermayer@medunigraz.at.
authors.forename: Barbara
authors.initials: B
authors.lastname: Obermayer-Pietsch
authors.affiliation: Department of Nuclear MedicineUniversity Medical Centre Ljubljana, Zaloška 7, 1525 Ljubljana, SloveniaFaculty of MedicineUniversity of Ljubljana, Vrazov trg 2, 1104 Ljubljana, SloveniaDivision of Endocrinology and MetabolismDepartment of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Lerchbaum
mesh_terms: D005260:Female; D050031:Hashimoto Disease / Q000175:diagnosis* / Q000235:genetics*; D006801:Humans; D011085:Polycystic Ovary Syndrome / Q000175:diagnosis* / Q000235:genetics*; D011110:Polymorphism, Genetic / Q000235:genetics; D013961:Thyroid Gland / Q000473:pathology*