ABSTRACTObjectives:To assess serum anti-Müllerian hormone (AMH) levels as an ovarian reserve marker in adolescent girls with autoimmune thyroiditis (AIT) and explore the relationship of this marker with autoimmunity and thyroid function biomarkers.Subjects and methods:This study included 96 adolescent girls with newly diagnosed AIT and 96 healthy, age- and sex-matched controls. All participants were evaluated with detailed history taking and physical examination, thyroid ultrasound, and measurement of levels of thyroid-stimulating hormone (TSH), free thyroxin (FT4), free triiodothyronine (FT3), antithyroid peroxidase antibodies (TPOAb), antithyroglobulin antibody (TGAb), estradiol, total testosterone, and anti-Müllerian hormone (AMH) levels. The LH/FSH ratio was also calculated. Among 96 patients evaluated, 78 were overtly hypothyroid and 18 were euthyroid. AMH levels were significantly lower in participants with overt hypothyroidism and euthyroidism compared with controls.Results:Serum levels of AMH correlated negatively with age, body mass index (BMI) standard deviation score (SDS), and TPOAb, TGAb, and TSH levels but positively with FT4 levels. In multivariate analysis, AMH levels correlated significantly with age (odds ratio [OR] = 1.65, 95% confidence interval [CI] 1.18-2.32, p = 0.05), BMI SDS (OR = 2.3, 95% CI, 2.23-3.50, p = 0.01), TSH (OR = 2.43, 95% CI 1.5-2.8, p = 0.01), and TPOAb (OR = 4.1, 95% CI 3.26-8.75, p = 0.001).Conclusions:Ovarian reserve of adolescent girls with AIT, as measured by serum AMH levels, is affected by thyroid autoimmunity and hypothyroidism, indicating a possible need for ovarian reserve monitoring in these patients.