Peripheral precocious puberty due to inadvertent exposure to topical oestradiol gel and review of the literature.

IntroductionTopical oestradiol gel is now widely used in hormone replacement therapy (HRT), but the risk of inadvertent secondary transfer to children is under-recognised. While accidental exposure to testosterone gels has been documented, oestradiol gel transfer as a cause of precocious puberty in prepubertal girls is rare.We undertook a 20-year literature review and discuss the case of a 5-year-old girl presented with Tanner stage 3 breast development, pubic hair stage 2, growth acceleration and mood changes. Laboratory evaluation revealed markedly elevated oestradiol levels with suppressed gonadotrophins, consistent with peripheral precocious puberty. Bone age was advanced by 4 years 6 months. Imaging, karyotype, endocrine and dermatology investigations excluded central precocious puberty, ovarian or adrenal tumours and McCune-Albright syndrome. History, previously not disclosed, revealed daily co-sleeping with her mother, who had been applying oestradiol gel to her upper arms for 18 months as part of HRT. No other oestrogen sources were identified. Maternal oestradiol gel was discontinued and replaced with a transdermal patch. The child's oestradiol levels normalised and pubertal signs regressed over subsequent months.This review highlights a rare but important cause of peripheral precocious puberty due to unintentional transfer of topical oestradiol gel through routine parent-child contact, including co-sleeping. As topical hormone therapies become increasingly common, clinicians must counsel patients on safe application practices and consider exogenous hormone exposure in children presenting with unexplained pubertal development. Switching caregivers from gel to patch formulations can reverse hormone excess in exposed children.