Primary hypothyroidism is frequently associated with delayed puberty. However, precocious puberty is known to occur in some rare cases of hypothyroidism untreated for a long time.
A female patient with Down syndrome aged 2 years and 9 months was referred with the symptom of vaginal
bleeding continuing for 1 week. In her history, there were no symptoms suggesting trauma, foreign body, urinary tract infection or intracranial mass. The patient exhibited the phenotypic features of Down syndrome and her height and weight were within 5%-25% percentiles and 25%-50% percentiles, respectively, regarding the growth curves generated for children with Down syndrome. Breast development was at Tanner stage 3 bilaterally, and she had no axillary or pubic hairs. Suprapubic ultrasonography revealed cystic lesions in the right lower quadrant and left adnexial region. She was diagnosed with Hashimoto thyroiditis as result of the tests and was started on Na lthyroxine replacement therapy, and all examination findings relevant to precocious puberty and laboratory parameters returned to normal in the 6th month of the treatment.