Hypogonadotropic Hypogonadism in Mosaic Turner Syndrome: A Rare and Atypical Presentation

Turner syndrome is the most common sex chromosome abnormality in girls, typically resulting from complete or partial monosomy of the X chromosome. It is typically associated with short stature and hypergonadotropichypogonadism, due to gonadal dysgenesis and defective ovarian feedback on the hypothalamic-pituitary axis. In this context, elevated levels of follicle stimulating hormone (FSH) and luteinizing hormone(LH)are expected during puberty.The occurrence of hypogonadotropichypogonadism in a patient with Turner syndrome is highly unusual and may lead to diagnostic confusion, as it contradicts the expected endocrine pattern.We report a rare case of a 13 year and 9 month old girl referred for evaluation of delayedpubertyandshortstature,with no dysmorphic features.Hormonal analysis revealed low gonadotropin levels. Cytogenetictestingshowedamosaickaryotype(45, X/46, XX), and pituitaryMRIrevealed anterior pituitaryhypoplasia, consistent with central hypogonadism, the evaluation of the remaining pituitary axes, including the thyrotropic,corticotropic, and somatotropic axes, revealed preserved endocrine function.This case highlights the diagnostic challenges posed by atypical presentations of Turner syndrome. Although hypergonadotropic hypogonadism is the norm, the coexistence of central hypogonadism especially in mosaic cases should be considered. Clinicians must remain vigilant for hypothalamic or pituitary dysfunction in Turner patients with unexpected hormonal findings to ensure accurate diagnosis and optimal management.